Iraqi security forces said they had found the bodies of 20 bus drivers who had been kidnapped north of Baghdad earlier today.

Police had put the number of bus drivers kidnapped in Miqdadiya, 100km northeast of the capital, at 12, but Major General Ahmed al-Awad said 20 bodies had been found after gunmen snatched a group of drivers from a station.

Mr Awad told state television that security forces released three kidnap victims during a search operation.

Meanwhile, US Defence Secretary Donald Rumsfeld arrived in Baghdad today for an unannounced visit to US commanders.

During his visit, Mr Rumsfeld said security in Iraq now depends as much on the Iraqi government's political success as on beating the insurgency militarily.

Mr Rumsfeld arrived in Iraq the day after suicide bombers killed 16 people outside the main entrance of the heavily fortified Green Zone government compound, where he was due to hold his meetings.

That attack coincided with a parliamentary session at which one lawmaker warned that civil war was close.

Mr Rumsfeld said that it had not reached the point yet where a reduction in the number of US troops in Iraq was possible.

He said that US commanders and Iraqi officials must undertake a comprehensive review of needs on the ground before the United States can consider reducing troop levels.

A 129,000-strong US force is serving in Iraq more than three years into the war in which about 2,500 US troops have died.