(Updates with latest death toll, adds details)

RAMADI, Iraq, April 6 (Reuters) - A truck bomb exploded in the volatile Iraqi city of Ramadi on Friday, killing at least 15 people and releasing chlorine gas into the air, police and security sources said.

Police Colonel Tareq Dulaimi from Ramadi said the bomb, which targeted a police patrol, wounded at least 30 people. He said several people were also choking from the gas.

There has been a spate of chlorine truck bomb attacks in recent months, mainly in western Anbar province. Ramadi is the capital of Anbar, stronghold of the Sunni Arab insurgency and a haven for al Qaeda.

U.S. commanders and Iraqi police have blamed al Qaeda militants for several of the chlorine attacks.

Chlorine gas was widely used in World War One but its use in insurgent attacks in Iraq has particular resonance there. Saddam Hussein attacked Kurdish areas with chemical weapons in the 1980s during the Iran-Iraq war.

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