"The Islamists are today criss-crossing the town's market and arresting girls not wearing a veil," El Mehdi Cisse, a resident of the Djinguerey Ber neighbourhood, told AFP by phone.

Any woman seen on the street after 11pm would be taken to prison and must pay a fine, he added, citing an edict from the Ansar Dine Islamists, who have ties with Al-Qaeda in the Islamic Maghreb.

"Since last night, they've visited imams to tell them that from now on all girls must be decently dressed," said another resident Boubacar Yattara.

The imams were also told of the creation of a "women's prison" and different fines for contravening "Islamic law", one imam said.

The move is the latest in a series hardline rules imposed by jihadists and radical Islamists in Mali's north, where sharia law has been enforced.

Amnesty International on Thursday decried what it said was an increase in violence and severe punishments in the north.

They cited cases in which they had stoned to death an unwed couple, carried out amputations on suspected robbers and flogged cigarette smokers.

A March 22 coup in the capital Bamako led to chaos in the north, with Tuareg rebels and Islamists quick to exploit the army's weakened hold on the expansive desert part of the west African country.

Ansar Dine fighters have also destroyed several ancient Muslim sites and shrines in Timbuktu, declaring the relics "haram", or forbidden.