In Baghdad, gunmen threw a hand grenade at an army vehicle in the mainly Sunni district of Adhamiya, killing three soldiers and setting the car ablaze, city security spokesman Major General Qassim al-Moussawi said.

When chased by police and soldiers, the attackers threw three more grenades, killing three policemen and wounding ten people, he said.

An Interior Ministry source put the Adhamiya death toll at 16. The source said gunmen killed three soldiers using silenced guns. While police and civil defense crews rushed to the scene, five roadside bombs exploded within a radius of one kilometer, killing three civilians and wounding 14, among them seven policemen and civil defense workers.

In Falluja, 50 km west of Baghdad, the scene of heavy fighting with U.S. forces in the past, a roadside bomb targeting an Iraqi army patrol killed three soldiers and wounded four others in a northeast district, a police source said.

In a separate incident, another roadside bomb went off near an Iraqi army patrol, wounding five soldiers.

And in Shirqat, 300 km north of Baghdad, a suicide car bomber targeting an Iraqi army base killed three soldiers and wounded eight, army and police sources said.

The U.S. military is reducing its forces in Iraq to 50,000 troops by August 31, when they will formally move to a more advisory role supporting Iraq's security forces.

There have been almost daily bombing and shooting attacks in which hundreds of Iraqis have died, although overall violence has dropped sharply since 2006-07, when thousands of Iraqis were killed in sectarian bloodletting.