Francois Molins spoke during a press conference a day after three women were dramatically arrested, including a teen whose father owned a car loaded with gas canisters that was abandoned in central Paris. No detonators were in the car, discovered on Sunday morning

The women who spearheaded the failed plot included a 19-year-old whose written pledge of allegiance to the Islamic State group was found by police, a security official said on Friday.

The teen, Ines Madani, stabbed a police officer with a knife and was shot in the leg on Thursday evening in a raid south of Paris, police said.

One of the women detained in a police raid, referred to as Sarah H and who was wearing a veil during the police raid, was betrothed separately to two French extremists who carried out deadly attacks this year, the Paris prosecutor said.

Sarah H was engaged to Larossi Abballa, who killed two police officials in Magnanville in June and filmed the aftermath on Facebook Live before dying in a police raid.

She was also betrothed to Adel Kermiche, who slit the throat of an elderly French priest during morning Mass, and died in July, Molins added.

Mr Molins did not say when she was engaged to either man.

France's interior minister described the pursuit as "a race against time" to find Madani and the two women with her before they struck. Another of the women had been engaged to the extremist who killed two French police officials earlier this year before he was shot to death, two officials said.

A man arrested on Thursday also had ties to the dead jihadi, Larossi Abballa, who filmed himself on Facebook Live pledging allegiance to IS as he sat in the home of the couple he had killed, one of the officials said.

"There's a group that has been annihilated, but there are others," French president Francois Hollande said on Friday. "Information we were able to get from our intelligence services allowed us to act before it was too late."

One of the security officials said French authorities found a note on Madani declaring allegiance to the extremist group, which has called on followers to attack France. The official said Madani was taken to hospital.

Another official, who also cannot be identified when speaking about the investigation, said Madani had pulled a knife during the raid outside a small apartment building near the Boussy-Saint-Antoine train station.

In video filmed by a neighbor, a veiled woman, her face uncovered, is seen being carried away by police as she cries out "Allahu Akbar" or "God is the Greatest" in Arabic.

Five women and two men have been arrested in the case.

The car loaded with gas cylinders belonged to Madani's father, who flagged her to police on Sunday 14 hours after the vehicle was discovered. Since then, authorities have worked frantically to untangle the relationships among the group and thwart what they increasingly feared was another plot.

More than one-third of the nearly 700 French citizens who have reached the war zones of Iraq and Syria are women, according to government figures. And officials have said for months that those being recruited by Islamic State in France are increasingly adolescent girls and young women.

Security around Paris was visibly higher on Friday as the investigation widened.

A bomb squad, sniffer dogs and a scanner were deployed when a gas canister with a timer but no detonator was found outside a police station on Friday morning in the suburb town of La Plaine Saint Denis, just north of Paris, and near the Stade de France in Saint-Denis, a local police official said.

In a sign of fraying nerves, the son of a gas delivery driver was briefly detained because he had canisters in his car. Elsewhere, police in Paris used explosives to disable an illegally parked motorcycle.

Explosive gas canisters filled with nails were the weapon used in bomb attacks by Algerian extremists on Paris in the 1990s.