Twenty suspected Taleban militants have been killed in a bloody clash with US and Afghan forces in southern Afghanistan, the US military has said. One Afghan policemen was also killed and six US soldiers injured in the fighting in Zabul province on Tuesday. The clash began when gunmen fired on coalition forces investigating the beating of a local man, the US said. The US has about 18,000 troops hunting al-Qaeda and Taleban militiamen, mainly in the south and east of Afghanistan. A US military statement said helicopters and aircraft were called in during the clashes with about 25 suspected militants in Zabul\'s Deh Chopan district. Five Afghan police officers were also wounded and six of the insurgents, including a village head with suspected Taleban links, were detained, it said. Four injured US soldiers have been taken to hospital in Germany in stable condition. The two others have returned to duty.