Paris - France is to open de-radicalisation centres in every region to identify would-be Islamist extremists before they join jihadi groups, tackling what it called the most serious threat to the country since the Second World War.
The Socialist government announced the creation of a dozen “reinsertion and citizenship centres” across France as part of an 80-point plan to fight home-grown terrorism, which it unveiled on Monday.
The two-year plan includes a string of anti-terror measures aimed at combatting the growing number of young people in France drawn to jihadi groups, and better detecting those tempted to join at an early stage.
Manuel Valls, the French prime minister, said fighting the appeal of “deadly” doctrines and their "ideology of chaos" was the greatest challenge the country faced in more than 70 years and required a response from all sections of society.
“The radicalisation of part of our youth, seduced by a deadly antisocial model, is in my view the most serious challenge we have faced since the second world war because it deeply damages the republican pact," said Mr Valls, flanked by the interior and justice ministers, as well as those of defence, education, health, culture, youth and sports.
“Radicalisation and terrorism are linked. We are faced with a stubborn phenomenon that has widely spread through society and which threatens it because it could expand massively,” he warned.
The plan, which will cost an additional €40 million by 2018 on top of the current funding, aims to double existing efforts to try to help people already in jihadist networks or those likely to join such groups.
The centres, the first of which is due to open this summer, will house young people who “could have repented and who we will test the sincerity and willingness to be reintegrated back into society for the long term”, Mr Valls said.
At least half of the new centres will hold those deemed by a judge to be at risk of radicalisation but cannot be placed in detention, he added, without clarifying.
The government has previously said there will be two types of centre: one for voluntary would-be extremists who have repented, and another for radicalised individuals who theoretically could be imprisoned for having sought to reach extremists groups abroad but failed to actually reach war zones in Iraq or Syria.
However, some experts fear the centres could end up being counterproductive.
"I am hostile to these 'jihad academies'," Asiem El Difraoui, a researcher told Le Parisien. "Some radicals have become masters in the art of dissimulation. All it takes is one leader to turn the whole group."
Mr Valls admitted that France was "feeling its way" in dealing with the issue, as are all Western countries.
The measures are a response to the deaths of 147 people in jihadist attacks in France last year, including those against Charlie Hebdo and a Jewish supermarket in January, and then at the Bataclan concert hall and bars and restaurants in eastern Paris in November.
Both attacks were carried out mainly by French citizens who had become radicalised and fought abroad alongside jihadist groups.
The new measures were announced as the trial opened in Brussels of a terror cell with alleged links to the Paris and recent Brussels attacks - in which 32 died.
In all 16 men are accused of trying to kill police officers following a raid in the Belgian town of Verviers in January 2015 in which two suspects were killed. Abdelhamid Abaaoud, the slain suspected ringleader of November's Paris attacks, is thought to have been the mastermind.
Assault rifles, munitions and chemical products that could have been used to make four kilograms of TATP were found. Seven defendants were in court and nine are being tried in absentia.
France estimates that some 9,300 people have been radicalised in France and that around 2,000 French nationals or residents have travelled to Syria and Iraq to fight with Islamic State, with more than 600 still there.
Monday's plan will also extend an existing programme to provide an anonymous freephone number for members of the public to report extremist suspects to the police and help for families of those who have been radicalised.
It also provides for tighter measures to protect sensitive potential terror targets, from nuclear power plants to public transport.
French intelligence services will receive more money and staff, with particular emphasis on detecting and tracking extremism in prison.
Mr Valls also announced the creation of a scientific committee to research the causes of radicalisation and terrorism, with university grants for related studies.