Women living under Isis’s self-declared ‘caliphate’ are being subjected to 'brutal, abnormal sex acts' and are becoming too scared to leave their homes, a local activist group has claimed.

Many women and young girls are being forced to marry Isis militants in the group’s defacto capital of Raqqa, in Syria, and are then reportedly beaten and abused by their husbands.

The Syrian activist group Raqqa is Being Slaughtered Silently (RBSS) says universities have been closed by Isis and women are banned from travelling to other areas to study. In a report on its website, the group said Isis fighters began searching for wives after taking over a swathe of the city. It says militants introduced a series of "crackdowns" designed to coerce women into marriage, such as prohibiting them from travelling or working without a male relative.

Palmyra after Isis

Abu Mohammed Hussam, one of the RBSS activists living outside of Raqqa, said women who walk around without male guardians are constantly harassed.

He said girls and women between the ages of nine and 50 are sent to special ‘education centres’ to learn the Koran and given lessons on how to be good wives.

Women with their children in Raqqa (Pic: Raqqa is being Slaughtered Silently)

The RBSS report claimed Isis members took advantage of poverty-stricken families by offering high dowries in exchange for marrying their daughters.

Mr Hussam said he spoke with three women between the ages of 19 and 29 who have allegedly been abused by Isis members. One woman told him she was hospitalised after a fighter she was forced to marry sexually assaulted her.

A woman is seen walking down a street in Raqqa (Pic: Raqqa is being Slaughtered Silently)

He told The Independent: “Some women say that foreign fighters are the worst, like monsters. Some of them say they're asking for strange things. They are also looking to marry young girls”.

He said fighters will often take more than one wife and search for 'sabaya' – women who have been kidnapped and sold into sexual slavery.

A report on the RBSS website states that fear of being attacked and sexually assaulted are making women scared to leave their homes.

“All of these factors and circumstances mentioned above have formed a panic and fear to the girls and women of Raqqa, which the houses became their current tombs," it reads.

Islamic State fighters in Raqqa (AP)

The report come a month after a 10,000 word manifesto detailing the role of women in the jihadist group and emphasising their role as wives, mothers and homemakers was uploaded by the all-female Al-Khanssaa Brigade’s media wing.

The revealing document is being treated as a more accurate representation of what is expected of women under the group’s Iraqi and Syrian strongholds.