Explosions killed four Iraqis and wounded five others, and American soldiers arrested a man described as an "executioner" for Saddam Hussein, the U.S. military reported Friday.

South of Baghdad, in the holy Shiite Muslim city of Najaf, 50,000 faithful gathered for ceremonies marking the 40th day since the car bomb assassination of revered cleric Mohammed Baqir al-Hakim (search).

The U.S. military said the man they labeled a Saddam executioner was caught in a raid in Baquoba, 40 miles northeast of Baghdad. Maj. Josslyn Aberle, a spokeswoman for the 4th Infantry Division, did not identify the man by name. She said he and another man, identified as a former general, were arrested in an overnight raid. The alleged executioner will be turned over to Iraqi police for questioning and trial if his identity is verified, Aberle said.

Overnight, the U.S. military reported soldiers of the 101st Airborne Division witnessed two Iraqis killed as they were trying to place a roadside bomb in Kirkuk, 145 miles northeast of Baghdad. Two other Iraqis were killed south of Tikrit when a bomb exploded at a traffic circle. Tikrit, 120 miles north of Baghdad, is Saddam's hometown.

Raids late Thursday and early Friday uncovered a large cache of weapons in the town of Salman Pak, including five rocket-propelled grenade launchers, two dozen grenades for the weapons, two anti-aircraft missiles and more than 72,000 heavy machine gun bullets. Soldiers also arrested three people carrying documents linking them to the Saddam Fedayeen (search), the regime's former militia, Aberle said.

Also Friday, attackers in a car hurled a hand grenade at two U.S. Army vehicles outside the Al-Karma Hotel in Baghdad, witnesses said. Five Iraqis, including four teenagers, were wounded. No American soldiers were hurt, but they did uncover an unexploded roadside bomb planted in the median of the street near where the grenade attack took place.

The U.S. Central Command (search) reported, meanwhile, that a 1st Armored Division soldier drowned in a swimming pool in Baghdad on Friday. It gave no other details.

In Najaf, 110 miles south of Baghdad, the huge crowd marched into the city chanting anti-Saddam slogans, some people beating their chests in a traditional Shiite gesture of mourning. Others chanted pledges of support for Abdel-Aziz al-Hakim, the dead cleric's brother and a member of the U.S.-appointed Governing Council.

"The enemies of the Iraqi people from the remnants of the former regime and their allies are criminals and terrorists and they are determined to commit their crimes against the Iraqi people, who will not remain silent," al-Hakim said.

He also was critical of the U.S.-led occupation authority's attempts to pacify the country, which is still rattled by violence nearly six months after Saddam was ousted.

"The adopted policies by the occupation forces in dealing with the security situation are wrong and must be reconsidered and abandoned. Political parties must be counted on to handle this difficult task," he said.

Iraqi police, the Badr Brigade -- the banned military wing of the Supreme Council for the Islamic Revolution in Iraq -- and uniformed soldiers of the Patriotic Union of Kurdistan provided security at the memorial services. The slain al-Hakim founded the Supreme Council while in Iranian exile. His brother has since taken over leadership.

Black flags of mourning were strung on buildings throughout Najaf, the site of the Imam Ali shrine, the holiest Shiite location in Iraq.

Al-Hakim was killed in a car bombing Aug. 29 in Najaf. The attack left more than 80 others dead and more than 140 wounded and was the single deadliest attack under the U.S.-led occupation.

Speaking at al-Hakim's grave site, Jalal Talabani, head of the Patriotic Union of Kurdistan and member of the Governing Council, described al-Hakim's death as a "national disaster for Iraq and Muslims" and a huge loss for Iraqis. He called for unity between Sunnis and Shiites.

Mohsen Abdul Hamid, another member of the Governing Council, warned of plans to sow discord between Shiites and Sunnis.