French police have arrested a 16-year-old teenager in the eastern city of Strasbourg as part of an investigation into a suspected plot to attack security forces and possibly the presidential Elysee Palace, according to judicial sources.
The teenager is the fifth person to be arrested in relation to the investigation.
According to France's TF1 television, he is believed to be a high school student of Chechen origin and was arrested at his parents' home.
His arrest comes after three adults and another teenager were taken into custody on 26 April.
Interior Minister Christophe Castaner says they would have carried out an "extremely violent terror attack".
The attack was allegedly planned to coincide with the start of the Muslim holy month of Ramadan, which began in France on Monday. Officials said the suspects had scouted out areas near the Elysee and a police station in the Parisian suburb of Aulnay-sous-Bois.
Intelligence services suspect the teenager of being in charge of publishing a video claiming allegiance to the Islamic State group according to TF1, a claim confirmed by the judicial source.
"Several projects were envisioned, all against security forces," including those stationed outside the Elysee, the source said.
Of the four arrested initially, one is a 17-year-old who served a year in prison after being convicted of trying to join jihadist fighters in Syria in 2017.
The three others, aged 26, 38 and 39, were previously known to police only for petty crimes.
France remains on alert since a wave of domestic jihadist attacks in 2015 which have killed more than 250 people.
At the end of March, two men were indicted in Paris on suspicion of planning an attack on a school or a police officer.