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 ISIS’ 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: Radicalized women were at the heart of each.

It is not yet 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, the authorities take it as a given that women are now part of ISIS’ European strategy, said François Molins, the Paris prosecutor who is in charge of terrorism investigations nationwide.

“The terrorist organization 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 extremist groups.

Those being apprehended now are often younger and blur traditional gender roles between male and female 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 ISIS militants and bear their children.

Today’s female, European jihadists are also far from the 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.

Farhad Khosrokhavar, a sociologist at the École des Hautes Études en Sciences Sociales in Paris, said adolescent and postadolescent 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 ISIS 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 jihadist 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, Molins said.

These somewhat contradictory elements suggest that the threat is coming from a more independent, feminist type of jihadist, 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 ISIS. In both cases, there is the possibility, experts say, that ISIS and other groups are using women to goad men into staging attacks.

Recent comments made by Rachid Kassim, a Frenchman who joined ISIS 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 Wafa Messaoud, a Muslim chaplain, who works with Muslim women in French prisons.

Among those in prison for extremist activities, “there are many converts,” Messaoud said. She added that ISIS 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, Inès 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 told investigators that she had bought the gas canisters, according to French news reports.

The New York Times