In fresh attacks, three more US troops have been killed in Iraq, the American military announced on Tuesday, raising to 30 the number of deaths it has suffered this month.

A marine "died Sunday from wounds sustained due to enemy action" during an operation south of Baghdad, and a soldier died Monday in similar circumstances in the restive western province of Anbar, a military statement said.

Eight people were killed in violence in Baghdad and the northern Iraqi city of Mosul Tuesday, security and medical sources said.

Five policemen died and three were wounded in firefights with gunmen in southern districts of Mosul, a flashpoint city where Sunni insurgents have established a base, Major Mohammed Ahmed said.

In a major crackdown launched in the past few weeks against the Mahdi Army -- the militia headed by Sadr and considered the biggest security threat to Iraq by the Pentagon -- more than 600 fighters and 16 militia leaders have been detained, the military said.

"There are currently over 600 illegal Jaish al-Mahdi (JAM) militia in detention awaiting prosecution from the government of Iraq," a statement said.

It said Iraqi and US forces had also detained 16 high-level militiamen and killed one commander in a series of operations against the Mahdi Army, known for its fiercely anti-American stance.