Car bombs exploded during morning rush hour in two business districts of Baghdad Tuesday, killing as many as seven people and wounding 19, including three American soldiers, officials said.

The worst blast occurred near a cinema in al-Nasr Square, a main intersection of shops, offices and apartment buildings, sending a huge plume of black smoke up into the sky near the east side of the Tigris River, said an Associated Press reporter at the scene.

A police officer with the Interior Ministry said on condition of anonymity that at least seven people were killed and 16 wounded by a suicide car bomb as it exploded just as a US military convoy of Humvees and armoured vehicles was passing. Al-Arabiya television confirmed those casualty figures.

A US military spokeswoman, Captain Kelly Lewis, confirmed the car bomb attack, saying it apparently targeted an Iraqi army patrol, wounding at least 10 Iraqis and three American soldiers. The hurt Iraqis included security forces and civilians, said Lewis.

Also Tuesday, US forces backed by helicopter gunships and warplanes swept through an area of western Iraq near the Syrian border for a third day, raiding desert outposts and safe houses belonging to insurgents, the US military said.

As many as 100 militants have been killed since Operation Matador, one of the largest American military offensives in Iraq in six months, began on Saturday night in the border town of Qaim, 320 kilometres west of Baghdad, the military said.

At least three US Marines have been killed in the offensive, which was hunting for followers of Iraq's most wanted terrorist, Abu Musab al-Zarqawi, leader of al-Qaida in Iraq, said US officials.

A Los Angeles Times reporter embedded with the offensive said 20 American troops also were wounded, but the US military could not immediately confirm that.

The offensive comes amid a surge of militant attacks across Iraq, often targeting Iraqi security forces and civilians, since the country's new government was announced on April 28. As of Monday, at least 1,606 members of the US military had died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

(China Daily May 11, 2005)