Women from Britain, Australia and Malaysia have reportedly travelled to Iraq and Syria to serve as 'comfort women' for Isis militants, a phenomenon which has become known as "sexual jihad."

Intelligence authorities in Kuala Lumpur have confirmed that at least three Malaysian females have travelled to the Islamic State, the caliphate established by the Sunni extremists. One of the women is said to be in her 30s while another is in her 40s.

The concept of sexual jihad previously surfaced in conflict zones such as Syria and Egypt when the countries were reeling under political turmoil. During the crisis, women are said to have offered sexual comforts to fighters to boost their morale.

"These [Malaysian] women are believed to have offered themselves in sexual comfort roles to Isis fighters who are attempting to establish Islamic rule in the Middle East" an intelligence official, who did not wish to be identified, told the Malaysian Insider.

"This concept may seem controversial but it has arisen as certain Muslim women here are showing sympathy for the Isis struggle."

The official added that intelligence information shared from Britain and elsewhere reveal that Australian and British females are also performing sexual jihad for the militants.

At least 600 Britons, including several women, are estimated to be in the war zones in Iraq and Syria. Some estimates quote a much higher figure.

"This figure also includes British Muslim women who are not fighting on the front line, but are still involved by performing sexual jihad. Australian intelligence officials have revealed that more than 100 Australian Muslims are in Syria fighting alongside Isis," the intelligence official added.

Earlier reports had suggested that the Iraqi Sunni extremists had called upon Muslim women in Mosul to perform sexual jihad to satisfy the male insurgents engaged in battle.