Meanwhile CNN president Jeff Zucher said there is a "total and complete lack of understanding" at the White House about the seriousness of their attacks on the media. Mr Trump has previously called US news outlets the "enemy of the people".

President Trump is still planning to travel to Wisconsin for a rally this evening in support of Republican Governor Scott Walker, Bill Shine, the White House Communications Director, has told CNN. 

Alexander Soros, the son of George Soros, said in an opinion piece for The New York Times that his father had long faced verbal criticism and threats over his involvement in politics, "but something changed in 2016".

"Before that, the vitriol he faced was largely confined to the extremist fringes, among white supremacists and nationalists who sought to undermine the very foundations of democracy. But with Donald Trump’s presidential campaign, things got worse," he wrote.

He placed direct responsibility with those who sent the devices, but added: "I cannot see it divorced from the new normal of political demonisation that plagues us today."

Telegraph columnist Rob Crilly says the president must do more than condemn bombs in the mail. Read his piece in full here.

Democratic Representative Maxine Waters said police have informed her that her office in Washington was also the target of a suspicious package.

A spokesman for the New York Police Department said a suspicious package sent to Governor Andrew Cuomo’s office was not a bomb. The spokesman said it is unrelated to the other devices.

President Trump has called for "unity" in his first public comments on the suspicious packages appearing across the US today.

Speaking from the White House, he said: "The safety of Americans is my highest and absolute priority. As we speak the packages are being inspected by experts and a major investigation is under way."

Mr Trump said he was briefed by the FBI, Department of Justice and Security Service on the attacks. "The full weight of the US government is being deployed" to investigate, he said. "We will spare no expense or resource in this effort."

"In these times we have to unify, we have to come together and send one very clear, strong unmistakable message – that acts or threats of political violence of any kind have no place in the United States of America."

"This egregious conduct is abhorrent to everything we hold dear as Americans. We are extremely angry, upset, unhappy about what we witnessed this morning and we will get to the bottom of it."

Melania Trump, the First Lady, addressed the day’s events during an event at the White House. 

“We can not tolerate those cowardly attacks and I strongly condemn all who choose violence,” she said. She also thanked the Secret Service and law enforcement officials for their response. 

Florida police have confirmed that they are investigating a suspicious package near the offices of Democratic Congresswoman Debbie Wasserman Schultz.

Local media showed images of a bomb squad unit from the Broward Sheriff’s Office, which confirmed it was at her building in the south Florida town of Sunrise, around 30 miles north of Miami.

Ms Wasserman Schultz had a five-year stint as the Democratic Party chair but resigned following a leak of emails in 2016 suggesting an insider attempt to hobble the campaign of Hillary Clinton’s rival in the White House primaries, Bernie Sanders.

It is not known if she was in her office at the time. She was expected to appear later with Mrs Clinton at a campaign event.

Mayor Bill De Blasio said: "At a time when there is a lot of hatred and division, it does not make sense to exacerbate it." 

Addressing all "public officials", Mr De Blasio urged: "Don’t encourage violence, don’t encourage hatred, don’t encourage attacks on media.

"Unfortunately this atmosphere of hatred is contributing to the choices people are making to turn to violence, there’s no question about it. Let’s turn down the temperature."

New York Governor, Andrew Cuomo, said: "We are weeks from an election and that’s obviously in the air and that’s an obvious factor.

"We have political differences and that’s good for democracy. What is not good is overheated rhetoric, extremism that pushes people to violence. And  at the end of the day… we’re all Americans. 

"Keeping the dialect civil is very important. And for elected leaders who in many ways set the tone, that is especially important."

New York’s Democratic governor Andrew Cuomo announced that a suspicious device was also sent to his office in Manhattan.

"A device has been sent to my office in Manhattan," Mr Cuomo told the press conference. "The device sent to my office has been identified and is being handled as we speak."

The governor, who is a trenchant critic of Mr Trump and who is seeking a third term as chief executive of the country’s fourth most populous state, said he "wouldn’t be at all surprised" if more devices show up.

Bryan Paarmann, the FBI special agent in charge, said that "so far the devices have been what appeared to be pipe bombs".

Commissioner John Miller revealed that after the first device was found on Monday, law enforcement officials began to take "proactive steps". These involved visiting politicians and media outlets – and in fact New York police officers were instructing staff at CNN’s newsroom to be on the look out for suspicious packages when the device was discovered.

New York’s Governor, Andrew Cuomo, said New Yorkers should remember that the city has the best law enforcement agencies "on the globe". "We should take comfort in that level of professionalism that we have in this city and in this state," he said. "As everyone is aware there are a number of packages that have been received."

Mr Cuomo added: "This is the world that we live in. Terrorism, the attempt to spread fear, is the world that we live in. It is heightened lately…This is a circumstance of who we are and where we are.

"Terrorism only works if you let it work. We are resilient and we will not allow these terrorist thugs to change the way we live our lives. They fail unless we allow them to win and we will not allow them to win"

Mr Cuomo also stressed that New Yorkers will see a heightened police presence across the city as a precautionary measure.

"You shouldn’t be alarmed… But we will not let terrorism win. Not today, not ever," he said.

Bill De Blasio, the New York Mayor, said: "What we saw here today was an effort to terrorise. This clearly is an act of terror attempting to undermine our free press and leaders of this country through acts of violence.

"I want to make very clear that the people of New York City will not be intimidated, that we are going to go about our lives undeterred because the very concept of terrorism is to change us and we will not allow that to happen. You cannot be terrorised if you refuse to allow the terrorists to win. People of this city have shown time and again that they stand up in the face of these efforts to intimidate."

Mr De Blasio said he wanted to reassure residents that there would be an increased police presence in the city. But he added: "we do not at this time have credible and specific threats in New York City". 

James O’Neill, the NYPD Commissioner, has given a press briefing on the latest developments from today’s events.

He said a "live explosive device" and an envelope containing white powder were found in the CNN building today. 

"We’ve seen this before. We’ve seen worse," he said. "We will not be intimidated and we will bring these perpetrators to justice".

NYPD’s chief of counter terrorism said the explosive device sent to CNN’s headquarters in New York appeared to be sent by the same "individual, or individuals" who mailed pipe bombs to George Soros, Hillary Clinton and former President Barack Obama.

John Miller and FBI officials said the devices all appeared to be crude pipe bombs. The New York device was black and had wires.

Mr Miller said it started on Monday night with the device sent to Mr Soros. He said they’re looking at the devices as a pattern, and they have not made any arrests. No one was injured by any of the devices.

The San Diego Union Tribune has also been evacuated, but it is unclear whether this a linked incident.

The newspaper said its staff were evacuated after a stack of suspicious looking packages were spotted near the front doors.

The building also includes the office of Democrat senator Kamala Harris, who is expected to run in 2020.

Senate Majority Leader Mitch McConnell said on Wednesday the targeting of Democratic politicians Hillary Clinton and Barack Obama with potential explosives amounted to acts of "domestic terrorism."

"I stand with all Americans in condemning today’s attempted acts of domestic terrorism," the Republican senator said in a statement.

Paul Ryan, the House Speaker, also condemned the sending of the suspicious packages just 13 days before crucial midterm elections, saying "we cannot tolerate any attempt to terrorise public figures."

Hillary Clinton has spoken about the suspect package that was addressed to her during an event in Florida.

The former Democratic presidential candidate said she and her family were doing "fine" and said the Secret Service intercepted the suspicious package "long before" it got to their home

"Every day we are grateful for their service and commitment," she told the audience. "But it is a troubling time isn’t it? It’s a time of deep divisions and we have to do everything we can to bring our country together.

"We also have to elect candidates who will try to do the same, who will set goals that will lift up every single Floridian and American, who will understand what the challenges are today.

"Usually when people ask me how I’m doing, which happens quite often, I say well as a person I’m great but as an American I’m worried. I worry about the direction of our country."

Ms Clinton attending events in Florida ahead of November’s midterm elections when the package was delivered to her New York home.

Speaking at an event Mike Pence, the US Vice President, said those responsible for today’s attacks "will be brought to justice".

The device has now been removed from the Time Warner Center, Harriet Alexander reports. It’s being driven away from the city, followed by helicopters. The chief commissioner of NYPD has just gone in to the building, accompanied by the city’s counter terrorism chief.

Florida police say they are probing a suspicious package near the office of a Democrat lawmaker. It follows earlier reports that Representative Debbie Wasserman Schultz’s Florida office was evacuated.

President Trump has not yet tweeted about the incidents himself. However his press secretary has issued a statement rebuking the attacks.

Harriet Alexander is on the ground in New York: "We’ve just seen a group of perhaps a dozen more NYPD officers enter the building, some with sniffer dogs. All eyes are on what we believe to be the bomb squad truck. The device is expected to be brought out to that truck.

"Jeff Zucker, the CNN president, has just sent a second email saying that the NYPD remain in the building.  He also said searches have been carried out at their offices worldwide, but it appears only their New York office affected."

The suspicious package sent to the CNN newsroom was addressed to the Former CIA director John Brennan, the network said. Mr Brennan, a regular critic of President Trump, is in fact a contributor of MSNBC – not CNN.

The package was sent to ’10 Columbus Circle’. This is not the official address for the CNN newsroom but the address which comes up if you search for the network’s New York headquarters online.

Harriet Alexander, The Telegraph’s US Correspondent, reports from New York: "Here at Columbus Circle, there is a heavy police presence, and constant sirens. The bomb squad is here, with sniffer dogs. The latest news appears to be that a pipe bomb was sent to a CNN correspondent, and intercepted in the mail room.

"The building has been evacuated. Jeff Zucker, the president of the media company, has just emailed all staff to tell them they are  “working with authorities to determine the severity of the situation”. He said that other CNN offices are also being searched around the world, as a precaution. Remarkably, the subway beneath the Time Warner Building is still open and operating normally, albeit with dozens of police on the platforms."

Sarah Sanders, the White House press secretary, has been asked about the apparent bombs on camera by a reporter for a network of local broadcasters. The journalist tweeted out the clip. 

Ms Sanders said: “The White House condemns these types of horrific and despicable acts and will work with law enforcement to make sure anybody responsible is punished to the full extent of the law."  She added: “Certainly it’s okay to disagree in politics but it’s never okay to take action against another individual and we certainly don’t want to see that happen.”

The suspicious package delivered to the Time Warner building in New York is being removed by the city’s bomb squad. It has been placed in a bomb containment unit on a truck which will take it to the Bronx. It is understood that this can contain the explosion in case it detonated during its disposal.

The device sent to the Time Warner Center, which houses CNN’s New York newsroom, was constructed with a pipe and wires, according to a New York Police Department source. Law enforcement authorities are treating the device as a real explosive. The device was discovered in the mailroom of Time Warner Center. It is unclear who the package was addressed to.

“We condemn the attempted violent attacks recently made against President Obama, President Clinton, Secretary Clinton, and other public figures,” said Sarah Sanders, the White House press secretary. "These terrorising acts are despicable, and anyone responsible will be held accountable to the fullest extent of the law. The United States Secret Service and other law enforcement agencies are investigating and will take all appropriate actions to protect anyone threatened by these cowards."

US network’s CNN New York office has been evacuated after receiving a suspicious package.

CNN reporters broadcasted from the street outside their bureau in a bustling part of Midtown near Central Park, saying they heard the fire alarm and the lights went off, before they walked down the stairs.

The network has been repeatedly criticised for Republicans for its coverage of the Trump administration over the last two years.

"It was a package mailed into the building that caught the security screening," said CNN presenter Jim Sciutto.