France is to beef up its domestic spy agency, create a national anti-terror prosecutor and a special unit to monitor radicalised inmates when they leave prison, the prime minister announced on Friday.

Edouard Philippe announced the plan as authorities were set to deploy 110,000 police and security forces across France this weekend to protect citizens from attack on Bastille Day and during street parties should the national football team win the World Cup on Sunday.

The 32 measures were the latest effort to thwart extremist violence after a string of deadly terror attacks over the past three years that have left 246 people dead. 

The plan includes the creation of a new terrorism prosecutor’s office and focuses leadership of counter-terrorism activities with the DGSI domestic intelligence agency, France’s MI5.

A special profiling unit will be created to better identify and understand extremists at risk of turning violent.

"The threat has evolved. We need to adapt ourselves," said Mr Philippe from DGSI headquarters in Levallois-Perret, west of Paris.

“Today the terrorist is no longer remotely-controlled by cells in Syria,” he said. The threat now came from “petty criminals, psychologically weak, indoctrinated or self-radicalised people".

With prisons seen as breeding grounds for radicalisation, Mr Philippe said tracking extremist ex-inmates was among France’s greatest future challenges, given that around 450 are due for release by the end of next year.

The national anti-terror prosecution office will now take the lead from a special unit of the Paris prosecutor’s office, as it was necessary to have a “prosecutor dedicated to fighting terrorism full time,” he said. Critics have warned the new office could create blind spots from criminal networks with terror links.

A senatorial report out this week said French authorities were now better equipped to tackle terrorism but underlined “real failings” in the fight against “Muslim radicalism” and Salafism. It also called for mayors to have access to files on dangerous radicals in their area.

Mr Philippe said that mayors could obtain “confidential information” if need be but there would be no free access to terror databases. “This isn’t about turning mayors in France into intelligence agents,” he said.

Security is especially high for Bastille Day celebrations this weekend, with 12,000 police out in Paris alone and another 4,000 on World Cup final on Sunday, where giant “fan zones” pose a major security headache. Around 90,000 people are expected to watch the game on Sunday night under the Eiffel Tower, with around 230 such screens installed around the country.

France is still on tenterhooks two years after 86 people were mown down by a van in the Mediterranean coastal resort of Nice as thousands had gathered for the traditional firework display.

"Everything is being done so the French can live these festive moments with peace of mind, despite the terrorist threat which remains at a high level,” said Gerard Collomb, the interior minister.

"The goal is to guarantee that these events go off smoothly… that the party not be spoiled by such tragedies," said Paris police chief Michel Delpuech.

Police have not faced the prospect of such huge gatherings in the capital since July 12, 1998, when up to 1.5 million fans amassed on the Champs Elysees after France won its first World Cup title.

Hundreds of thousands more took to the streets for Bastille Day two days later.