Yemen\'s armed forces have shelled tribal areas in the central Marib province, after tribesmen shot down a military helicopter, killing nine soldiers. Witnesses told Arab Today that the army used heavy artillery and tanks during the operation against gunmen suspected of involvement in blowing up oil pipelines, in the town of Wadi Obeidah. Nine soldiers, including the commander of 107th Infantry Brigade was killed when a military helicopter was shot down earlier on Tuesday.