BAQUOBA, Iraq — Insurgents used a roadside bomb to blow up another U.S. Bradley Fighting Vehicle yesterday, killing two American soldiers and wounding four others.

The attack in southwestern Baghdad marked the second time in five days that a Bradley was heavily damaged by a roadside bomb. An attack Thursday in northern Baghdad killed seven U.S. soldiers.

The heavily armored Bradleys, which weigh about 25 tons, were thought to be less vulnerable to homemade bombs, known in military terms as IEDS, or improvised explosive devices. But recent deadly attacks suggest that insurgents had shifted to larger bombs or found a way to penetrate the Bradley's armor.

At least 1,355 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.