BAGHDAD (Reuters) - A U.S. soldier in Iraq was arrested on Sunday on suspicion of shooting dead a civilian contractor on the U.S. military's Camp Speicher, its main base in northern Iraq, a U.S. military spokesman said.

The shooting took place on Sunday at around 8.30 am (0530 GMT), U.S. military spokesman for north Iraq Derrick Cheng said.

"A U.S. Soldier has been identified and detained in the alleged shooting incident of a civilian contractor here on ... Speicher," he said. "The civilian contractor later died of wounds. We offer our sincere condolences to the family."

Speicher is on the outskirts of the Iraqi city of Tikrit, 150 km (95 miles) north of Baghdad. Cheng did not give further details of the shooting, which he said was under investigation.

In May, a U.S. soldier shot dead five fellow soldiers at a military clinic in Baghdad, an incident that triggered some soul searching in the U.S. military about the effects of stress on troops who do serial deployments.

(Reporting by Tim Cocks; Editing by Ralph Boulton)