Police vehicles blocked off the main road and officers fired shots in the air as people approached checkpoints ahead of Friday afternoon prayers, the major day of worship in Islam.

"We are afraid of violence after prayers in Kufa," a Sadr stronghold, one officer said.

In another sign of the lingering tensions in Najaf, around 250 locals earlier demonstrated to demand Sadr and his Mehdi Army leave the holy city, whose centre was devastated by weeks of bloody fighting with US troops.

An AFP correspondent on the scene said the small procession marched for an hour towards the Imam Ali shrine, whose surroundings were the scene of intense combat between Sadr's militia and US troops until last week.