BEIRUT — The Islamic State group has imposed an “Afghan-style” dress code on men in its Syrian stronghold Raqqa to help its fighters blend into the civilian population, a monitor and activists said Monday.

“For more than two weeks, Afghan-style clothing… has been imposed by Daesh,” said Abu Mohamed, an activist with the “Raqqa is Being Slaughtered Silently” group, using the Arabic acronym for the Islamic State.

“Anyone who does not comply faces prison and fine,” he told AFP.

The new restriction comes as a Kurdish-Arab alliance of fighters nears Raqa, backed by the US-led coalition launching airstrikes against IS.

The rule “is an attempt to make it harder for airplanes and the Kurdish forces… to distinguish between civilians and Daesh members,” Abu Mohamed said.

The Syrian Observatory for Human Rights, a Britain-based monitor of the war, also reported the new rule in Raqqa.

“The Islamic State has imposed Afghan-style dress on residents of Raqqa so that informants giving coordinates to the US-led coalition will not be able to distinguish between civilians and fighters,” Observatory director Rami Abdel Rahman told AFP.

Abu Mohamed said there was a “state of alert” in Raqqa, with new checkpoints springing up and the Islamic State arresting anyone who describes the situation as dire.

“Prices are skyrocketing and there is no electricity or water,” he told AFP.

The Observatory also said civilians and the families of Islamic State families were attempting to flee into Raqqa province from neighboring Aleppo, where the Islamic State group is under assault in the east.

“Thousands of families in recent days have tried to reach the administrative borders of Raqqa province, along with around 120 families of fighters and commanders of IS,” the monitor said.

The Kurdish-Arab Syrian Democratic Forces alliance advancing towards Raqqa on Monday cut a key supply route between the city and IS-held territory in Deir El-Zor province to the east.

The alliance is now eight kilometers (five miles) from Raqqa to the northeast, according to the Observatory.

It said Islamic State was preventing civilians from entering the province “but granted families of its fighters” a document allowing “passage to Raqqa city by boat as ground transportation is now impossible because the bridges across the Euphrates have been destroyed”.