Paris (AFP) - Three teenagers linked to an Islamic State group jihadist have been arrested around Paris in the past week as investigators probe the use of an encrypted messaging app to plot attacks in France, judicial sources said Wednesday.
On Wednesday, a teenager was arrested in a dawn raid on his home in northeastern Paris as part of an investigation into the network of French extremist Rachid Kassim.
Investigators said the youth, aged 14 or 15, was in touch with Kassim on the encrypted Telegram app and had "put himself forward for a terrorist act".
His arrest came four days after a 15-year-old picked up in the upmarket western Paris suburb of Rueil-Malmaison was remanded in custody on terror charges, a source confirmed to AFP.
The 15-year-old, who was already on a watchlist of known radicals, was also arrested over his links to Kassim, who is suspected of using Telegram to direct attacks on France from IS-controlled territory in Iraq or Syria.
The source said the youth's online messages suggested he may have been planning to stage an attack. Earlier this year he was charged with disseminating IS propaganda on the internet.
Their arrests bring to three the number of minors detained in various parts of the French capital within a week as the authorities scramble to tamp down home-grown jihadist violence that is increasingly drawing in teens.
On Monday, a 15-year-old from eastern Paris was charged with conspiring to commit terrorist acts after describing plans on Telegram to carry out a knife attack, sources said.
Kassim, a 29-year-old former social worker from the Loire valley who has appeared in several IS propaganda videos, is believed to have been a key influence on all three youths.
He is also suspected of ordering or inciting the killing of a police couple in their home west of Paris in June as well as the murder of an elderly priest in a Normandy church in July.
- 'Younger and younger' -
Interior Minister Bernard Cazeneuve said Wednesday that the intelligence services were "working harder than ever" to prevent assaults incited by "a number of characters in Syria who used encrypted methods" to spur on supporters, who are "getting younger and younger."
Kassim was also in contact with an all-female gang of radicals who have been charged with planning another attack after an apparent failed attempt to blow up a car packed with gas cylinders near Paris's Notre Dame cathedral.
The three women were also believed to be planning an attack on a train station or on the police. Two of them had previously been on a police watchlist for their extremist views.
Islamic extremists have targeted France repeatedly in the last two years.
An assault on satirical weekly Charlie Hebdo in January 2015 was followed by a rampage by IS gunmen and suicide bombers in Paris in November that killed 130 people.
More recently, a grisly truck attack on a crowd in Nice in July left 86 dead.
French Prime Minister Manuel Valls on Sunday said the terror threat was at a "maximum" and that the authorities were foiling attacks and smashing jihadist networks "every day".
Valls said that around 15,000 people were known to police in France as having been radicalised, up from a previous estimate of 10,000.
Former president Nicolas Sarkozy, who is seeking the conservative nomination in next year's presidential election, has called for all known radicals to be placed in detention.
Cazeneuve dismissed the idea on Wednesday.
"Once you let people know they are under surveillance they go to ground."