Islamic State is using increasing numbers of women to evade security measures and spearhead a wave of attacks across Europe and the Islamic world as it loses territory in the Middle East.

Previously, female members of Isis have been confined to support roles and kept away from the battlefield. However, this policy appears to have been reversed in the summer, as military pressure on its main strongholds in Iraq, Syria and Libya intensified and substantial territory began to be lost. Researchers describe a “drastic U-turn”.​

Officials have repeatedly warned that Isis would launch attacks as it retreated from earlier gains. Since August, a series of plots involving women have been uncovered by security authorities in Europe and north Africa.

The new tactic poses a challenge for security organisations which already have difficulty penetrating extremist networks and identifying potential attackers. “It’s a concern … There is constant evolution as the pressures on [Isis] increase, so we are not complacent​,” said one western European security official.

A plot in Paris in September, involving four women aged between 19 and 39, received significant media coverage. The cell, organised by a known Isis militant in France, was the first to be entirely female. Two of the women had been listed as potential security risks by French intelligence agencies after attempting to reach Syria to join Isis. A third was recently married to a militant shot dead by police on the outskirts of Paris in June, after he stabbed two police officials to death at their home.

“If at first it appeared that women were confined to family and domestic chores by the terrorist organisation, it must be noted that this view is now completely outdated,” François Molins, a French prosecutor, told reporters​ after the four were arrested.

​But a series of other plots around the world, which involve women playing “combat” roles, received less attention. In August, Isis was reported to have deployed at least one female suicide bomber in Libya, while last month 10 alleged female attackers were arrested in Morocco. All were in their teens, had sworn allegiance to Isis, and were in possession of bomb-making material, ​officials said.

Terrorists are focusing [recruitment] efforts on minors who are female. That is very worrying for all of us Abdelhak Khiame, Morocco

The women, believed to have been planning a series of suicide attacks, “got in touch with [Isis] elements via the internet and were brainwashed into committing destructive acts targeting … tourist sites in particular,” said Abdelhak Khiame, who leads Morocco’s Central Bureau of Judicial Investigations.

“This is the first time we have found a terrorist cell that was entirely composed of women. Terrorists are focusing [recruitment] efforts on minors who are female. That is very worrying for all of us. It’s an alarm bell,” Khiame said.

Women have long played a role in Islamic militancy, and have​ been deployed in frontline positions​ before. Palestinian groups have used women suicide attackers. So, too, have organisations in central Asia and the Caucasus. However, senior commanders of al-Qaida, the extremist group responsible for the 9/11 attacks, has consistently made clear its opposition to women taking part in combat activities, insisting that they should support male “mujahideen” and the broader struggle, rather than physically take up arms themselves.

The ruling has not always been obeyed. Al-Qaida’s own affiliate in Iraq deployed a female suicide bomber in 2005 to attack a hotel in Amman, Jordan.​ The decision prompted much criticism within extremist circles.

Isis, which shares broad ideological objectives with al-Qaida but differs dramatically over strategy and tactics, initially restricted the many thousands of female volunteers it attracted from Europe and the Islamic world to support activities. “Thus far, Isis has stifled the role of women in the ‘caliphate’ by limiting them to the house, ensuring they raise the next generation of jihadi militants and provide for their husbands,” said Rachel Bryson, ​of the Centre on Religion and Geopolitics in London.

There have been some ​exceptions: ​female “lone wolf” attackers who attacked without official sanction from the group, ​and one major affiliate – Boko Haram in west Africa – ​which has systematically used young women as suicide attackers.

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The recent change “would suggest the group is starting to heavily feel the pressure from the action taken against it,” Bryson said.

In recent months, Isis has lost significant ground in Libya, and its core territory in Iraq and Syria is now threatened. Offensives are now under way against ​the cities of​ Raqqa, ​the provincial centre in Syria ​seen as the headquarters of the group, and Mosul, the biggest single urban centre under Isis control and the seat of the “caliphate” declared by its leader, Abu Bakr al-Baghdadi, more than two years ago.

As important as the loss of territory is the diminishing population under Isis authority. Although some revenue is earned from oil and other resources, most funds are raised through “taxation” of individuals, communities and businesses.

Analysts are split over the impact of military defeat on Isis. Some believe the organisation will be able to continue to attract support because of its past record of victories, with volunteers taking the view that it needs help now more than ever. Other experts believe that the appeal of Isis will be seriously weakened.

Bryson said: “As [Isis] and others start to lose more ground, their pool of recruits will grow smaller, meaning that they’ll need more women to take up combat roles. Furthermore, Isis knows that the death of a woman evokes a larger response worldwide than that of a man, and for Isis’s PR machine increasing the group’s media platform is an attractive prospect.”