(adds U.S. military spokesman) BAGHDAD, May 29 (Reuters) - Two U.S. military personnel were killed when their helicopter came down under enemy fire north of Baghdad and six more died when a column of vehicles heading to the crash site was ambushed, the U.S. military said on Tuesday. The deaths on Monday brought the U.S. military death toll in Iraq to 112 this month, making May the deadliest for 2007 and equalling the record set in December 2006. A total of 3,463 U.S. soldiers have died since the March 2003 invasion. The worst month for U.S. forces was November 2004, when 137 were killed. U.S. military spokesman Lieutenant Colonel Garver said the helicopter came down in Diyala province, where 3,000 additional U.S. troops have been sent to fight mostly al Qaeda militants. "There was ground fire involved but we don't know how the helicopter went down," he said. He said a quick reaction force had been dispatched to secure the crash site. Six soldiers were killed when their vehicles were hit by roadside bombs. Militants have employed similar tactics in the past -- shooting down a helicopter and then ambushing the rescue force. Insurgents have shot down at least nine helicopters this year, killing 30 people, mainly American soldiers. Seven of those aircraft were U.S. military helicopters and the other two belonged to a private American security company. Diyala, a large, ethnically mixed region northeast of Baghdad, has seen some of the worst violence since the U.S.-led invasion in 2003. Violence has surged further in recent months since a crackdown in Baghdad forced militants to seek new bases.
