Paris (AFP) - A 17-year-old suspect in a foiled attack on a French military base was instructed by an Islamic State militant in Syria to "hit" France, a prosecutor said.
He and two other young men, aged 19 and 23, were charged and placed in detention on Friday after their plot to kidnap and behead a member of the French military on film was discovered by police.
The youngest -- identified as Ismael K. -- was told to carry out the attack by IS when it became clear he could not leave the country to wage jihad in Syria, Paris prosecutor Francois Molins said.
Four young men, including a former naval signalman, were arrested in dawn raids on Monday, suspected of "planning to commit a terrorist act" at a southern French military base at the end of this year or early 2016. A 16-year-old was quickly released.
They came into contact with each other via social networks and formed a plan to go to Syria to wage jihad alongside other IS extremists.
However, Ismael K.'s mother became concerned about his radicalisation and contacted the authorities. He was subsequently interviewed by counter-terrorism officials and was aware he was under surveillance.
For this reason, the trio used encrypted messaging systems and applications to communicate, the prosecutor said.
"There was in particular an exchange between Ismael K. and an individual currently fighting with IS in Syria who -- given it was impossible for him to leave France -- told him to 'hit on the ground in France'," the prosecutor said.
- 'Paramilitary' equipment found -
Ismael K. told investigators the plan was to attack the military base, "kill the soldiers there, decapitate the person in charge of the site, film the whole thing and flee to Syria".
The 23-year-old, identified as Djebril A., had served at the base and suggested striking around the New Year period as it was lightly defended at that time.
He joined the navy in June 2013 as a signalman, but suffered health problems and was eventually discharged in January 2015.
No weapons were found when searching their homes, although they had planned to arm themselves with handguns. Police did, however, seize "paramilitary" equipment -- including protective gloves used by jihadists in Iraq and Syria.
"Djebril A., Antoine F. and Ismael K. have several things in common -- as well as their young age," noted the prosecutor.
"They have never been convicted, had been educated to baccalaureate level (roughly equivalent to A-levels) and were strongly radicalised, in particular because they watched IS videos," Molins said.
France remains on high alert more than six months after jihadist attacks in January that claimed 17 lives and started with shootings at satirical magazine Charlie Hebdo.
"We are facing a terrorist threat that we have never seen before -- an external threat and an internal threat," Prime Minister Manuel Valls said on Thursday.
Although the foiled assault was planned around the first anniversary of the attacks on satirical magazine Charlie Hebdo that left 12 dead, none of the three alleged plotters indicated that the date was chosen deliberately for this reason.
The government says there are 1,850 French citizens or people living in France who are "implicated" in jihadist networks, and around 500 in Syria or Iraq.
France, which is home to Europe's largest Muslim population, has beefed up security, posting 30,000 police officers and soldiers outside 5,000 sites deemed sensitive such as schools and places of worship.
Authorities have also set up a hotline for friends or family concerned that someone could be tempted to wage jihad -- an effort that has yielded 2,500 leads.