PARIS — There was the parked car stuffed with gas canisters near the Notre Dame Cathedral, a possible effort to set off an explosion in the heart of Paris. There was the suspected plot to attack a train station in the Paris area. There was the effort by one of the Islamic State’s most prominent propagandists to recruit two young people in Nice, where an attacker had killed 86 people in July by running them down in a truck.

In France, where terrorist threats have become distressingly commonplace, these three episodes, all in the last month, stood out for one reason in particular: Radicalised women were at the heart of each.

It is not clear whether the phenomenon is a blip or the beginning of a trend in which women play a more active role in plotting and carrying out attacks on the West.

Security officials say they are concerned, and they are seeking to understand whether women are beginning to step up because so many men are under surveillance or in detention, or whether recruiters from terror groups are urging women on, in part, as a way to shame more men into taking action. They also wonder if it is part of a strategy to make Europeans feel that they should fear men and women alike.

Whatever the reasons, authorities take it as a given that women are now part of the Islamic State’s European strategy, said Mr Francois Molins, the Paris prosecutor who is in charge of terrorism investigations nationwide.

“The terrorist organisation not only uses men but also women, young women, who meet and develop their projects virtually,” he said.

Interviews with sociologists, lawyers, a Muslim chaplain and security experts suggest that the female extremists now drawing the attention of French law enforcement are different in several respects from earlier generations of women who joined or were attracted to Islamist groups.

Those being apprehended now are often younger and blur traditional gender roles between male and female Islamic extremists. They are more willing to take action themselves rather than to remain behind the scenes, in contrast to the women who have been leaving Western Europe for Syria to become wives of Islamic State fighters and bear their children.

Today’s female, European jihadis are also far from the Muslim extremist women from Chechnya and Iraq who became suicide bombers, almost always under the instruction and careful monitoring of male extremists. They are also far from earlier generations of non-Muslim radical women, such as those in the Red Brigades who embraced violence but often also had feminist ideals.

Professor Farhad Khosrokhavar, a sociologist at the cole des Hautes tudes en Sciences Sociales in Paris, said adolescent and post-adolescent boys and girls were increasingly involved in jihad in Europe. “And then we have a second category, which is women,” he said.

While the extremist women operating today in France typically proclaim loyalty to the Islamic State and have been in touch with people affiliated with the group, they appear to be acting with guidance and encouragement only from afar, from men either in Syria or in Europe.

Yet there are also continuing signs of the ways in which the male-dominated nature of Islamic jihadi culture defines the relationships between male and female extremists. Recruiters encourage online betrothals, and one of the women who were recently detained in the case of the train station attack had been engaged online to two different extremists, each of whom was killed in carrying out gruesome attacks in France, Mr Molins said.

These somewhat contradictory elements suggest that the threat is coming from a more independent, feminist type of jihadi, who sees herself as acting similarly to a man, but at the same time, some in this category of women also appear to be acting on instructions from male counterparts in the Islamic State. In both cases, there is the possibility, experts say, that the Islamic State and other groups are using women to goad men into staging attacks.

Recent comments made by Rachid Kassim, a Frenchman who joined the Islamic State and is now suspected of being one of its leading propagandists, suggest this kind of strategy might be at play.

“Women, sisters are going on the attack,” he wrote on the Telegram messaging application last month, after the gas canister plot was thwarted, according to the newspaper Le Monde. “Where are the brothers?” he added. Kassim is suspected of encouraging the women in that plot.

The recent plots in France led by women show both determination and the limits of their efforts. They also highlight what these women have in common: Some are converts, and some have tried to go to Syria but have been turned back. And the younger ones, especially, seem emotionally troubled, said Ms Wafa Messaoud, a Muslim chaplain, who works with Muslim women in French prisons.

Among those in prison for extremist activities, “there are many converts,” Ms Messaoud said. She added that the Islamic State seemed to be playing on the insecurities of the very young women being recruited and their desire to belong.

“They are young, in the middle of adolescence, and they have this psychological vulnerability,” she said.

In the recent episode in Paris, at least two women, Ins Madani, 19, and Ornella Gilligmann, 29, are suspected of placing full gas canisters in a car in early September, trying to light them and then leaving the car parked overnight near Notre Dame.

Gilligmann, who is a convert to Islam, told investigators that she had bought the gas canisters, according to French news reports. She was interested in going to Syria, said Mr Molins, the Paris prosecutor.

Madani supplied the car — it was her father’s, the Paris prosecutor said. She appears to have had connections to jihadi circles in Belgium, and investigators there wanted to question her about a network of extremists in Charleroi.

A few days after the car was found, police used phone taps and analysis of phone data to trace Madani and two other women to Boussy-Saint-Antoine, about 32km south of Paris. The three women are believed to have been planning an attack on a train station, French police said.

As they emerged from the house where they were hiding, one of the women, Sarah Hervouet, 23, stabbed a police officer in one of his shoulders as he sat in his police car, according to Mr Molins. Madani also tried to stab a police officer during her arrest, Mr Molins said. A third woman, Amal Sakaou, 39, did not try to attack the police, and almost nothing is known about her.

Hervouet is a convert to Islam, and she, too, wanted to go to Syria, Mr Molins said. She left for Syria in March last year, but never got there because Turkish authorities turned her back.

Mr Molins said that she had been betrothed first to the man who killed a police captain and his companion in June in Magnanville near Paris and then to Adel Kermiche, who went on to kill an 85-year-old priest in St-Etienne-du-Rouvray in July. There was no indication that she had ever met either of them face to face — both men were killed by police after their attacks — suggesting she had only interacted with them online. She subsequently appeared to be entering another online relationship, this time with another man who was arrested in connection with the Magnanville killing.

In the case in Nice, a 17-year-old and a 19-year-old were arrested on suspicion of having been in touch with Kassim, the Islamic State propagandist, on his encrypted Telegram channel and of having discussed a possible attack. But it appears that they changed their minds after the July 14 attack in Nice by a driver who was loyal to the Islamic State.

Certainly Frenchwomen have been fertile ground for Islamic State recruitment. Proportionately, more Frenchwomen than women from any other European country have gone to Syria and Iraq. And 40 per cent of the young people who have left France and are now in Syria are women, according to the French Interior Ministry.

While Mr Molins depicts the women as bound up with the Islamic State and directed by its male leadership, Prof Khosrokhavar said that in interviewing women who had gone to Syria or tried to get there, he had found evidence that the female recruits in this newest group were more independent than their predecessors.

These are young women who have grown up in Europe, where it is taken for granted that women can control much about their lives. The result is that their language is that of European feminists and yet, confusingly, was in the service of an ideology quite contrary to that, Prof Khosrokhavar said.

The women spoke of being stopped from achieving their goal of going to Syria as “an insult to their dignity and an insult to their autonomy,” he said.

The Muslim chaplain, Ms Messaoud, described the same trend as Mr Molins and Prof Khosrokhavar. Two years ago when she first started working in the prisons, she saw relatively few women who had embraced extremist views.

Today there are “more and more” who have been detained for a connection to extremist activities or individuals, she said. NEW YORK TIMES