Baghdad - Nine militiamen were killed in a US raid Sunday during fighting between US and Iraqi troops and loyalists of Shiite cleric Moqtada al-Sadr in their stronghold in east Baghad, while 42 abducted students were freed in the northern city of Mosul, the US military and eyewitnesses said.

A US gunship killed nine "criminals" in Sadr City in east Baghdad Sunday morning, the spokesman for the US-led multinational forces, Abdel Latif Rayan, told the Voices of Iraq (VOI) news agency.

Explosions and exchanges of fire have been heard in Sadr City since last night and this morning, eyewitnesses told Deutsche Presse- Agentur dpa.

US helicopters have been seen hovering over the area, the witnesses said.

US and Iraqi troops made incursions Saturday night into several areas in Sadr City and were engaged in fighting with gunmen, which caused fatalities.

"We are staying home as the clashes are still going on," an eyewitness said.

"Several main roads have been closed, which forced people to stay home. US snipers took position on rooftops of buildings," another witness said.

Medical sources said at least 20 people were killed and scores wounded in the fighting.

Last Sunday, al-Sadr ordered his fighters from the Mahdi Army militia to stop fighting government troops in Basra and other southern Iraqi cities.

The government launched on March 25 an offensive targeting mainly al-Sadr's militiamen in Basra but halted military operations after al-Sadr's move to halt fighting.

In the northern Nineveh province, the Iraqi army freed 42 students from the University of Mosul after they were abducted by insurgents in south-west Mosul, Iraq's Ministry of Defence said.

Gunmen stopped a bus carrying the students on the main highway between Baghdad and Mosul, local security officials said.

The students were seized and taken to an unknown place.

A plane of the multinational forces spotted a vehicle thought to carry the students, a US military statement said. Insurgents fled the scene after the vehicle was stopped.

The Iraqi army detained one of the insurgents at a house nearby.

Mosul, 400 kilometres north of Baghdad, has been central stage for Sunni insurgents, who fled Baghdad and surrounding areas and regrouped in northern Iraqi provinces. (dpa)