France plans to ban individuals linked to radical Islamist groups from leaving the country in a bid to prevent attacks by militants returning from the Middle East, according to a draft bill set to be unveiled on Wednesday.
France has seen a sharp rise this year in citizens going to join Islamic militants in Syria and now Iraq.
"We have a duty to react as almost 800 young people are involved," Interior Minister Bernard Cazeneuve told Tuesday's edition of the daily Le Parisien.
Of that figure, some 600 French nationals are either currently in Syria or planning to go there, he said.
French national Mehdi Nemmouche, arrested on charges of shooting dead four people in May at the Jewish Museum in Brussels, is suspected to have spent most of last year in Syria, fighting with Islamist rebels.
Cazeneuve said about 100 people were currently on their way back to France from Syria.
European governments have been tightening anti-terrorism laws over the last 18 months as the Syrian conflict enters its fourth year. In June, nine countries agreed to share more intelligence and take down radical websites to try to stop Europeans going to fight in Syria and bringing militancy home.
France has long been a target for Islamist militants because of its record as a colonial power in North Africa and problems integrating its large Muslim minority.
It has nonetheless had broad success at averting attacks due to its security apparatus and some of Europe's toughest anti-terrorism laws, which include the ability to hold a suspect for up to 96 hours without charge.
However, the ease of communication through social media and the growing turmoil in the Middle East have created new pressures, and the government has been criticized for not stopping French nationals as young as 14 from heading to Syria.
Discourage and prevent
"The objective of this bill is to increase the number of hurdles to discourage those who want to go and to stop them [from] actually going," said an Interior Ministry source.
Cazeneuve, who has already put in place a raft of policies this year to try to prevent young French Muslims from becoming radicalized, will unveil the bill to cabinet on Wednesday.
Primarily, it allows authorities to stop French nationals traveling overseas for an indefinite period if they are suspected of having firm links to a jihadist network.
Investigators will also now be able to hold and question individuals on a low threshold of evidence, under broad "suspicion of conspiring in relation to terrorism" - a measure intended to catch those who only associate loosely with other potential militants.
"Lone wolves are not necessarily as alone as we think," said the source.
The bill would also allow websites that condone terrorism to be blocked without a judge's approval.
The bill has raised civil rights concerns from some NGOs and lawmakers; the article on the internet has been sent to the European Commission to ensure it complies with EU legislation.
"France will not tolerate messages calling for or glorifying jihad to be shown on its soil with impunity," the draft says.
France's Muslim community is the biggest in the European Union, at 5 million. Many are marginalized, living with poor job prospects in grim, violence-ridden suburbs and housing estates.
But until Mohamed Merah, a young al-Qaeda-inspired gunman, killed seven people including three Jewish children in March 2013, France had not suffered a major attack since 1995, when the Algerian Armed Islamic Group bombed a Paris metro station, killing eight people and wounding dozens.