Updated

U.S. troops exchanged fire with Iraqi guerrillas who lobbed at least six mortar rounds at them in downtown Tikrit (search), and detained four people, including a suspected bomb maker, in a night of intense fighting early Thursday.

The mortar shells missed their targets, causing no injuries or damage, said Lt. Col. Steve Russell, commander of the 4th Infantry Division's (search) 1st Battalion, 22nd Regiment, which patrols Saddam Hussein's hometown of Tikrit, 120 miles 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 U.S. casualties, and that one attacker might have been killed. 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."

Also Thursday, U.S. troops acting on a tip from an Iraqi raided a house in Tikrit and detained four people, including a suspected bombmaker. Also seized were weapons and ammunition and a box of explosives, wires, clocks, nails and other bomb making material.

"It's not so much the amount, but the type of things we've got," Russell said.

Col. James Hickey, commander of the 4th Infantry's 1st Brigade, said the man, who was not identified, surrendered without a fight after being called out of his house. He was believed to be involved in bomb making activities in the Tikrit area. He was being interrogated, he said.

Hickey said the mortars that were fired into Tikrit were traced to a spot where the Charlie Company of the 1st Battalion, 22nd Regiment, was sent to investigate when it came under attack.

"The enemy is using very inaccurate, indiscipline fire. It gave us their location," he said. "We engulfed the area with tracer bullets. At the minimum, the enemy has withdrawn," he said, adding the guerrillas might have suffered casualties.