Baghdad, Iraq ? American troops and helicopters scoured the desert Thursday for two U.S. soldiers who were apparently abducted from an observation post in Baghdad. Ambushes and hostile fire elsewhere killed two U.S. soldiers and two Iraqi civilians and wounded eight other Americans.

A day after a U.S. Marine was killed responding to an ambush on Americans, reports of attacks on U.S. troops appeared almost hourly — too frequent for military press officers to keep up with. Most of the information came from witnesses at the scenes.

Iraqis celebrate an attack on a military convoy by throwing stones at the destroyed vehicles in the Youssefiyah area south of Baghdad, Iraq. A big truck hauler carrying a smaller vehicle Thursday was directly hit and caught fire. According to an eyewitness, four U.S. soldiers were in the damaged truck.

Officials played down the violence, but with shattered glass, blood stains and mangled vehicles littering the landscape, the upsurge in attacks is causing concern that the U.S.-led occupation of Iraq could be turning into a guerrilla war.

In the most serious attacks:

• A member of a U.S. special operations force was killed and eight were wounded Thursday morning by hostile fire southwest of Baghdad, the U.S. military said, giving no further details.
• A bomb exploded on the Baghdad airport road, killing a U.S. soldier and wounding another, the military said.
• Assailants threw grenades at a U.S. and Iraqi civilian convoy in west Baghdad, killing two Iraqi employees of the national electricity authority.