The mortar shells missed their targets, causing no injuries or damage, said Lt. Col. Steve Russell, commander of the 4th Infantry Division's 1st Battalion, 22nd Regiment, which patrols Saddam Hussein's hometown of Tikrit, 200 kilometers north of Baghdad.

An American reconnaissance patrol, responding to the mortar attack, was ambushed with small-arms fire and rocket-propelled grenades on the eastern bank of the Tigris River, directly opposite the 4th Infantry's sprawling headquarters in one of Saddam's former palaces.

Bradley fighting vehicles were called in as reinforcements, opening fire at the guerrillas as tracer bullets lit the night sky over Tikrit, which was plunged into darkness. An intense firefight ensued, and at least one house was on fire. Helicopters were heard hovering above.

Russell said there were no US casualties, and that one attacker might have been killed, as the rest of the guerrillas disappeared into the night.

"When you have such an incident, it appears to be a spike in activity. But in reality, it's a decline," Russell told said. "The enemy fire was not accurate at all. We see it as militarily insignificant."