Twelve Iraqi police have been killed dismantling what appeared to be a decoy roadside bomb near Kirkuk when another bomb exploded.

The policemen, including two officers, were killed on Wednesday when the device detonated near a fuel pipeline in the Badwan area about 15km north of Kirkuk, Iraqi police sources told Aljazeera.

The violence came as Secretary of State Condoleezza Rice's top deputy, Robert Zoellick, arrived in capital Baghdad on Wednesday on a one-day visit after Defence Secretary Donald Rumsfeld's trip to Iraq on Tuesday.

Car bomb

Also on Wednesday, four blasts were reported in Baghdad. 

A car bomb blast near a US military convoy seriously wounded four civilians, sources said.

The convoy, which included Iraqi National Guard troops, was hit near al-Amiriya, in western Baghdad, an Iraqi National Guard source said at the scene.

The blast destroyed a US Army Humvee and civilian cars, said a witness. The injured were evacuated by US helicopter.

Three other blasts struck US convoys in other parts of the city, including one near the international airport in western Baghdad, witnesses said.

In one of the blasts, a US military oil tanker was set ablaze in eastern Baghdad, witnesses said.

The truck was hit by a blast at 8.45am (0445 GMT) in a convoy on al-Kanat road, which cuts through eastern Baghdad and borders Sadr City, an Interior Ministry source said.

Separately, a police source reported an attack on a US military vehicle in the capital's Jadida district, but no further details were immediately available.

US military spokesmen had no immediate information about the attacks.

PHOTO CAPTION

An Iraqi man inspects an oil tanker damaged in an attack by unknown assailants close to the northern city of Kirkuk. (AFP)