Paris, French police investigating a car containing six gas cylinders in Paris have arrested three female suspects said to have been planning fresh attacks, shooting one of them in the process.
A police officer also suffered a knife wound during the arrest late Thursday of the three women -- aged 39, 23 and 19 -- who were preparing "new violent ... and imminent actions", according to Interior Minister Bernard Cazeneuve.
The woman shot, a daughter of the car's owner, had sworn allegiance to the Islamic State group, according to a source close to the investigation.
A local resident who saw the women just before their arrest in Boussy-Saint-Antoine, south of Paris, said they "seemed anxious, looking around them all the time".
When confronted, "one young women pulled out a knife and stabbed a police officer at stomach level", Joachim Fortes Sanchez, 21, told AFP. "It all happened very fast".
Four people -- two brothers and their girlfriends -- were already in custody over the car, found just a few hundred metres from the Notre Dame cathedral in central Paris, an area always thronged with tourists.
The first couple arrested, a 34-year-old man and a 29-year-old woman, have been held since Tuesday and are known to the security services for links to radical Islamists.
Police arrested the man's brother and his girlfriend, both aged 26, late Wednesday.
Authorities had said earlier they were searching for the two daughters of the owner of the grey Peugeot 607 abandoned on Sunday near Notre Dame, which draws millions of visitors every year.
A bar employee working near Notre Dame had first raised the alert on Sunday after noticing a gas cylinder on the back seat of the parked car, police said.
The car had no number plates and its hazard lights were flashing.
Although the cylinder on the back seat was empty, five full cylinders were discovered in the boot.
Three bottles of diesel fuel were also discovered in the vehicle, but police found no detonators.
"If it was an attack plot, the method was very strange," a police source said Thursday.
France is on high alert following a string of jihadist attacks, including last November's coordinated bloodshed in which Islamic State extremists killed 130 people.
Speaking on Thursday, President Francois Hollande referred to attack plots that have been foiled "in recent days", without elaborating.