Three US soldiers were killed and four were wounded in an explosion in a building in a volatile area northeast of Baghdad, the military said Saturday. The blast occurred while the Task Force Lightning soldiers were searching for a weapons cache and clearing a building in Diyala province, where US and Iraqi forces have been battling Sunni insurgents and Shiite militias for months around the city of Baqouba. The military said three soldiers were killed and four were wounded. Their identities were not released pending notification of relatives. The deaths raised to 36 the number of American troop deaths so far this month. At least 3,120 members have died since the Iraq war started in March 2003, according to an Associated Press count.