The military announced the deaths Tuesday of five U.S. soldiers in three separate roadside bomb explosions, pushing the number of U.S. fatalities since March 2003 past the 1,900 mark.

Four of the soldiers were assigned to the 2nd Marine Division, II Marine Expeditionary Force in Ramadi, 60 miles west of Baghdad. They were "conducting combat operations" and died in two separate incidents, said the military, declining to provide further details.

A fifth soldier belonged to the 18th Military Police Brigade and was killed 75 miles north of Baghdad when his vehicle was struck by an improvised explosive device, according to an official press release.

According to the Associated Press, the number of U.S combat deaths in Iraq stands at 1,904.

Separately, an American diplomat and three private security contractors died Monday in the northern city of Mosul when their armored SUV was attacked by a suicide car bomber, a Western official in Baghdad confirmed Tuesday morning.

Two others riding in the three-vehicle convoy -- which was departing a U.S. embassy satellite office in Mosul -- suffered minor injuries in the attack, which occurred at 9:49 a.m., the official said.

A lone driver pulled alongside the convoy and detonated an explosion next to the second vehicle. U.S. security personnel immediately cordoned the area and administered first aid, but the four appeared to have died instantly.

The diplomat killed in the attack was not named, but was described as a diplomatic security agent.

The incident marked the third U.S. diplomat killed since the 2003 invasion of Iraq. Diplomatic Security Agent Edward Seitz died in an October 2004 mortar attack on a U.S. base near Baghdad International Airport. And last November, James Mollen, a U.S. special adviser to Iraq's Ministry of Higher Education and Scientific Research, was shot to death near the capital's fortified Green Zone.

Fred Barbash reported from Washington.