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BAGHDAD, June 18 (Reuters) - U.S.-led coalition forces killed at least 20 militants after coming under attack during a series of raids in southern Iraq overnight, the U.S. military said on Monday.

It said the raids, targeting militants smuggling weapons from nearby Iran into Iraq, were carried out in the Shi'ite city of Amara and the nearby town of Majjar al-Kabir, both in Maysan province.

During the operations, coalition forces came under heavy small-arms fire and rocket-propelled grenade attacks in both places, the military said in a statement.

"Using appropriate escalation of force measures, ground forces were forced to use close air support to suppress the enemy fire. During the close air support, at least 20 terrorists were killed," it said.

Latif al-Tamimi, chief of the security committee on the Maysan provincial council, said 14 people and been killed and 35 wounded. He called the operation a "catastrophe", accusing troops of firing randomly.

British forces handed back security control of Maysan province to Iraqi security forces in April.

Overwhelmingly Shi'ite, Maysan, home to the Marsh Arabs and with large oil fields, has been spared much of the sectarian violence engulfing Baghdad and other areas that is pushing Iraq to the brink of all-out civil war.

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