BAGHDAD Ñ Sunni insurgents have succeeded in launching a major attack on a U.S. military base for the first time since the war began.

Iraqi insurgents fired mortars and rockets that struck a U.S. military base in the northern Iraqi city of Mosul on Tuesday in the most deadly attack on U.S. troops since the war in March 2003.

At least 24 people were killed and more than 60 were injured when the mortars and rockets exploded in a military dining room during lunch.

A U.S. military spokesman said 19 American soldiers were killed, Middle East Newsline reported. Another seven casualties were identified as employees of the U.S. Army contractor Halliburton and its subcontractors.

The Al Qaida-aligned Ansar Al Sunna claimed responsibility for the attack on the Forward Operating Base Marez. Ansar was linked to the Tawhid and Jihad group, led by Abu Mussib Al Zarqawi, regarded as the most lethal insurgent in Iraq.

U.S. Army Brig. Gen. Carter Ham, commander of Task Force Olympia, said those killed and wounded include U.S. military personnel, U.S. contractors, foreign-national contractors and Iraqi soldiers. Ham said the military has launched an investigation.

"In the chaos that followed that attack, there was no differentiation by nationality; whether one wore a uniform or civilian clothes," Ham said.

"They were all brothers-in-arms taking care of one another."

The base houses both U.S. and Iraqi troops. The U.S. force included soldiers from the Richmond-based 276th Engineer Battalion.

In November 2003. Sunni insurgents downed two U.S. Army Black Hawk helicopters in Mosul, killing 17 soldiers.