Guerrillas killed a U.S. soldier in a rocket-propelled grenade attack in central Baghdad (search) on Monday, and American forces arrested five men suspected of helping finance insurgents during raids on homes in Saddam Hussein's (search) home town of Tikrit (search).

The 1st Armored Division soldier died of his wounds early Monday in a military field hospital, the military reported. He was the 156th U.S. soldier to die in Iraq since President Bush declared an end to major combat on May 1. In heavy fighting before that date 138 soldiers were killed.

In Tikrit, the pre-dawn raids targeted three homes next to a highway which has seen 20 rocket-propelled grenade attacks on the U.S. military in the past two weeks. In the most recent attack Saturday, a guerrilla in a taxi fired a rocket-propelled grenade at an American convoy in downtown Tikrit, killing an Iraqi bystander and injuring two people.

"These individuals are involved in financing Fedayeen activity and organizing cells of resistance against U.S. forces," said Maj. Bryan Luke of the Army's 4th Infantry Division. No shots were fired in the early morning raid.

The 3 a.m. raid also captured assault rifles, pieces of an RPG and ammunition.

Secretary of State Colin Powell, on his first visit to Iraq, traveled to Halabja Monday. The city, on the border with Iran 150 miles northeast of Baghdad, was bombed and shelled with cyanide gas in March 1988 and some 5,000 Kurdish men, women and children were killed. Saddam carried out the attack to put down a Kurdish rebellion.

On Sunday, insurgents killed a U.S. soldier and wounded three outside the troubled city of Fallujah, a day after angry protesters fired weapons and called for violence against the American occupation to protest one of the most serious friendly fire incidents of the Iraq war.

The U.S. administrator for Iraq on Sunday commented publicly on the accidental killing of eight Iraqi policemen by U.S. forces who mistook them for guerrillas. He suggested victims' families might be compensated.

"The very regrettable incident in Fallujah is still under investigation by our military. We have expressed regrets for it publicly," L. Paul Bremer said at a news conference with Powell.

"When we have reached conclusions about how the incident came about, we'll take appropriate steps. In the past we have paid families ... where we felt it was appropriate, but this incident is still under investigation."

Powell arrived in Baghdad on Sunday for his first visit since the U.S.-led ouster of Saddam Hussein. He said he was encouraged by progress toward self-rule.

He stood fast against growing international pressure to quickly turn responsibility for running the country back to Iraqis.

"The worst thing that could happen is for us to push this process too quickly before the capacity for governance is there and the basis for legitimacy is there and see it fail," Powell said.

Earlier Sunday, Powell met with Hoshyar Zebari, Iraq's new foreign minister, and said the security situation remained challenging, with a "major new threat" coming from "terrorists who are trying to infiltrate into the country for the purpose of disrupting this whole process."

Fallujah, 30 miles west of Baghdad, has again become an especially dangerous place for the occupying forces after the friendly fire incident near the Jordanian Hospital, just west of the city.

Before Bremer issued his statement, the American military had apologized, but many in Fallujah rejected the overture and vowed to continue fighting U.S. forces.

Relations between people in Fallujah and U.S. forces have been extremely tense since shortly after the city was captured in April. U.S. troops came under almost daily attacks for two months after soldiers opened fire in late April on crowds of protesters in the city, killing 18 and injuring 78. The Americans said they were fired at first.