An al-Qaida-led militant group has demanded the United States call off its search for three U.S. soldiers abducted in Iraq, if the servicemen are to remain safe.

The "Islamic State of Iraq" issued its demand in an Internet posting Monday and said it is holding the soldiers.

The group has claimed responsibility for an attack Saturday south of Baghdad that killed four U.S. troops and led to the disappearance of the three others. They have been missing since.

The U.S. military said Monday it believes al-Qaida in Iraq or an affiliated group abducted the soldiers.

Thousands of U.S. troops, backed by helicopters and Iraqi forces, have been searching for the missing soldiers in an area south of Baghdad known as the "triangle of death." Iraqi officials say two militants were killed Monday during the operation.

In violence Monday, roadside bombings killed one Danish soldier near Basra and two U.S. service members in Baghdad. Two other U.S. soldiers were killed when their patrol came under fire southeast of Baghdad.

The U.S. military said another American soldier died of non-combat related causes.

Some information for this report was provided by AP and Reuters.