Three women arrested after a foiled plot to blow up a car packed with gas canisters near the Notre Dame cathedral in Paris were charged with terror offences on Monday and remanded in custody, the prosecutor's office said.
The women were detained last week after the discovery of the vehicle near Notre Dame on September 4. Police believe they were planning other attacks including striking a train station in the Paris area or targeting police.
The suspects -- named as 19-year-old Ines Madani, 23-year-old Sarah Hervouet and 39-year-old Amel Sakaou -- were brought before anti-terrorism judges on Monday and charged with involvement in a terrorist conspiracy.
The two youngest were also charged with plotting to kill public officials, while Hervouet's boyfriend was charged with failing to report a terrorist offence, a statement said.
The women are believed by police to have been spurred by repeated calls by the Islamic State group for attacks in France, with a known French IS recruiter believed to be linked to the case.
France is on heightened alert after two grisly attacks in July -- one in the southern resort of Nice, where a truck driver crushed 86 people to death and another in Normandy, where two men slit the throat of an elderly priest.
The country has been repeated targeted by Islamic extremists in the last two years, with an assault on the Charlie Hebdo satirical magazine in January 2015 followed by a rampage by gunmen in Paris in November.
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".
As many as 15,000 people were considered by French authorities as radicals who posed a potential threat, he added.
Sources close to the investigation said the women had discussed obtaining suicide belts or ramming cars filled with explosives into buildings.
One of them was found in possession of a letter professing her allegiance to IS, which ordered the carnage in Paris in November that left 130 people dead.
A 15-year-old boy arrested in eastern Paris at the weekend was also brought before investigating magistrates on Monday to be charged with conspiring to commit an "imminent" attack.
Unconfirmed reports in France that cited sources close to the investigation said the boy was intending to carry out a knife attack on the Couléé vert elevated walkway - Paris's equivalent of New York's High Line.
The youth had written to contacts on Telegram -- an encrypted messaging app widely used by jihadists to communicate -- of his plans to carry out a knife attack, sources said.