KIRKUK, Iraq (Reuters) -- A car bomb that targeted police assigned to protect northern Iraq's oil industry killed 10 people and wounded 23 others, police said, in the latest high-profile bombing in the country.
The casualties were piled into a police truck, and police travelling with the dead and wounded fired into the air to clear traffic ahead, a Reuters witness said.
Police initially said the blast was caused by a suicide bomber, but some now say the attackers may have detonated an explosives-laden vehicle, targeting a bus carrying police in the Iraqi city of Kirkuk, 250 kilometers north of Baghdad.
The oil-rich city is hotly disputed by Arabs, Turkomans, and ethnic Kurds, who consider it their ancestral capital.
Al-Qaeda has exploited territorial disputes in Iraq's north to remain effective even as violence has fallen elsewhere in the country. The Sunni Islamist group and other militants have also been able to hide in the remote rugged regions outside northern Iraq's cities.
Iraq's oil industry is particularly sensitive to attack, given that the country derives almost all of its revenue from its vast crude reserves, the world's third-largest. Oil infrastructure was not damaged in the blast.
Most attacks in Iraq's north are focused on the city of Mosul, where a truck bomb on April 10 killed two Iraqi policemen and five U.S. troops in the single deadliest incident for U.S. forces for over a year.
A series of high-profile blasts in Baghdad during the same period have led some analysts to point to political motives.
The attacks came before a national election due in December and as provincial councils finalize new coalitions and pick new governors after local polls in January, which saw allies of Prime Minister Nuri al-Maliki make major gains on a law and order platform.