Three women arrested in connection with a car loaded with gas cylinders found in a side road near Notre Dame cathedral had been planning an attack on a Paris railway station, the French interior ministry said.
“An alert has been issued to all stations but they had planned to attack the Gare de Lyon on Thursday,” a ministry official said on Friday after the arrests overnight.
The Gare de Lyon station is in the southeast of the capital, less than 3 kilometres from the cathedral which marks the centre.
The official also said the youngest of the three women, a 19 year-old whose father was the owner of the car and who was already suspected by police of wanting to go and fight for Islamic State in Syria, had written a letter pledging allegiance to the militant Islamist group.
The discovery on Saturday night of the Peugeot 607 laden with seven gas cylinders, six of them full, triggered a terrorism investigation and revived fears about further attacks in a country where Islamist militants have killed more than 230 people since January, 2015.
Scores of religiously radicalised people of French and other nationalities are in Syria and Iraq fighting for Islamic State. Many of those involved in recent attacks in France have either taken part in the fighting or had plans to.
France is among the countries bombing Islamic State strongholds, and the group has urged supporters to launch more attacks on French soil.
One of the women stabbed a police officer during her arrest before being shot and wounded, Interior Minister Bernard Cazeneuve said late on Thursday. Other officials said it was the teenager who attacked the officer.
TV footage showed a policeman leaving the scene of the arrests on the outskirts of Paris carrying a large knife.
Police sources said no detonator had been found in the car, though the vehicle also contained three jerry cans of diesel fuel.
When it was found in the early hours of Sunday morning the car had no registration plates and was left with its hazard lights flashing.
“These three women aged 39, 23 and 19 had been radicalised, were fanatics and were in all likelihood preparing an imminent, violent act,” Cazeneuve said in a televised statement. They bring to seven the number of people detained since Tuesday.
The arrests took place in Boussy-Saint-Antoine, some 30 km (20 miles) south-east of Paris.
The car’s owner was taken into custody earlier this week but later released. He had gone to police on Sunday to report that his daughter had disappeared with his car, officials said.