Two other high-ranking officers, a brigadier and a colonel, were gunned down in southern Baghdad, a police source said yesterday.

Meanwhile, a US soldier was sentenced to three years in prison for murdering a severely wounded Iraqi teenager earlier this year, the US military said.

Staff Sergeant Johnny Horne, 30, from Winston-Salem, North Carolina, had pleaded guilty to charges of murder and conspiracy to commit murder at a court martial in Baghdad on Friday. He was sentenced by a panel of seven senior soldiers after four hours of deliberation.

Four employees of the Ministry of Education were wounded when the bus taking them to work in Baghdad was raked by gunfire.

In the northern city of Mosul a car bomb exploded near a US military convoy wounding at least two passersby, witnesses and the US army said.

Security officials and civil servants have become prime targets for insurgents opposed to the US military occupation and to Iraqis working for the US-backed authorities.

Colonel Mohammed Abed said from his hospital bed that a fellow police colonel and another officer were killed in the ambush which left Abed and two others wounded.

"They blocked our way, shot us and took our cars," he said of the attack in Ash Sharqat, 110 km (70 miles) north of Tikrit.

A police source said gunmen in the south of Baghdad shot dead a police brigadier and a colonel, both of whom worked at the Interior Ministry. No further details were available.

A woman who survived the attack on the Education Ministry bus said in hospital: "We were on our way to work. We go the same way every day ... We don't know where the shooting came from." Two men and two women were wounded.

The yellow, unmarked city bus was riddled with bullet holes in the front and sides. Pools of blood lay inside.

JAILED FOR TORTURE
The convicted US soldier, who was also reduced in rank to private, will forfeit all pay and has been dishonorably discharged from the military, the military said in a statement.

The convictions stem from an incident on August 18 when Horne's unit came across a suspicious vehicle late at night in the poor Sadr City district of Baghdad.

US military officials have described the incident as a "mercy killing" after US soldiers opened fire on a garbage truck they suspected of being used by guerrilla bombers.

US forces clashed repeatedly in August with militiamen loyal to Shia cleric Moqtada al-Sadr. The sprawling Shia slum of Sadr City was a focal point of an uprising by Sadr followers.