TEMPO.CO, Jakarta - Islamic State (ISIS), the al-Qaeda offshoot that seized large swathes of northern Iraq last month, has warned women in the city of Mosul to wear full-face veils or risk severe punishment.

The Sunni insurgents, who have declared a caliphate in parts of Iraq and Syria and have threatened to march on Baghdad, also listed guidelines on how veils and clothes should be worn, part of a campaign to violently impose their radical brand of Islam.

"The conditions imposed on her clothes and grooming was only to end the pretext of debauchery resulting from grooming and overdressing," the group said in a statement.

"This is not a restriction on her freedom but to prevent her from falling into humiliation and vulgarity or to be a theatre for the eyes of those who are looking."

A cleric in Mosul told Reuters that ISIS gunmen had shown up at his mosque and ordered him to read their warning on loudspeakers when worshippers gather.

"Anyone who is not committed to this duty and is motivated by glamour will be subject to accountability and severe punishment to protect society from harm and to maintain the necessities of religion and protect it from debauchery," ISIS said.

The insurgents, formerly called the Islamic State of Iraq and the Levant, have been systematically stamping out any religious or cultural influences they deem non-Islamic since their lightning sweep through the north.

US military and Iraqi security officials estimate Isis has at least 3,000 fighters in Iraq, rising towards 20,000 when new recruits since last month's advance are included.

ISIS has provided guidelines on how women should dress in Mosul, one of Iraq's biggest cities. Their hands and feet must be covered, shapeless clothes that don't hug the body must be worn and perfume is prohibited. Women have also been told to never walk unaccompanied by a male guardian. ISIS has even ordered shopkeepers to cover their store mannequins with full-face veils.

The insurgents run vice patrols in Mosul that answer to a morality committee, which has shut the city's college of fine arts and physical education, knocked down statues of famous poets and banned smoking and water pipes.

REUTERS | INDAH P.