US military officials say a roadside bomb attack in Iraq on Saturday killed an American soldier - the first fatality in new armored vehicles designed to protect against such bombs.

Officials said Tuesday, the soldier was killed and three others were injured when an improvised explosive device (IED) detonated in the Arab Jabour area south of Baghdad. The soldiers were driving a "Mine Resistant Ambush Protected" vehicle - or MRAP - which has a V-shaped hull intended to deflect roadside bomb blasts.

U.S. military authorities say that, while the 1,500 MRAPs now in Iraq are designed to protect against roadside bombs, no vehicle can be counted on to withstand all attacks.

Roadside bomb attacks are responsible for a large percentage of U.S. casualties in Iraq. Defense Secretary Robert Gates said last year that MRAP vehicles are the military's highest acquisition priority.

Some information for this report was provided by AFP.