Iraq's new interim government is "illegitimate," militant Shiite cleric Muqtada al-Sadr said Sunday as he vowed to resist occupation forces to the "last drop of blood."

The renegade holy man led an uprising against coalition forces in April that left hundreds dead, but in recent weeks his followers had suggested they might transform their al-Mahdi Army (search) militia into a political party.

An Iraqi government spokesman said Monday that four men accused of involvement in the beheading of American businessman Nicholas Berg (search) had been arrested in May. The arrests had been announced before, and it was not immediately clear why the government announced them again.

The fate of Cpl. Wassef Ali Hassoun (search), a kidnapped U.S. Marine of Lebanese origin, remained unclear. A Web site statement Saturday attributed to the Ansar al-Sunna Army said he had been beheaded. But on Sunday, the group issued a statement on its own Web site saying the earlier declaration was false.

Hassoun's abduction was first reported June 27, when an Arab television station broadcast a videotape showing him blindfolded. A statement from militants threatened to kill him unless the United States released all Iraqis in "occupation jails."

Al-Sadr's latest comments apparently reversed earlier conciliatory statements he made to the government of Prime Minister Iyad Allawi (search).

"We pledge to the Iraqi people and the world to continue resisting oppression and occupation to our last drop of blood," al-Sadr said in a statement distributed Sunday by his office in the Shiite holy city of Najaf, where his al-Mahdi militia battled American troops until a cease-fire last month.

"Resistance is a legitimate right and not a crime to be punished," he said.

Previously, Al-Mahdi fighters accepted cease-fires in most Shiite areas after suffering huge losses at the hands of the Americans.

However, in his statement Sunday, the young cleric said, "There is no truce with the occupier and those who cooperate with it."

"We announce that the current government is illegitimate and illegal," al-Sadr said. "It's generally following the occupation. We demand complete sovereignty and independence by holding honest elections."

On June 12, al-Sadr had issued a statement saying he was ready for a dialogue with the new government if it worked to end the U.S. military presence.

It was unclear what prompted his apparent reversal, though al-Sadr has made contradictory statements in the past. Earlier Sunday, Allawi told ABC's "This Week" that he had met with al-Sadr representatives "who want to try and mediate."

"The position of the government is very clear," Allawi said. "There is no room for any militias to operate inside Iraq. Anything outside law and order is not tolerated, cannot be tolerated. The rule of law should prevail. Every one of us, every individual, starting from the president downward should be answerable to the law."

Al-Sadr launched his rebellion after the U.S.-led coalition administration closed his newspaper, arrested a top aide and announced a warrant charging him in the April 2003 murder of a rival cleric.

After nearly eight weeks of fighting, the Americans announced that they would leave it to the Iraqi government to deal with al-Sadr, including serving the arrest warrant.

In Basra, insurgents fired rockets at a government building, hitting nearby homes instead, police said. One person was killed and seven wounded. The attacks shortly after midnight were directed at the province's main offices near the center of the city.

The insurgents "missed and hit nearby homes instead," said Capt. Mushtaq Khaled of the Basra Police.

On Sunday, violence continued throughout the nation as Iraqi troops thwarted a car bombing outside their regional headquarters northeast of Baghdad, killing an attacker before could detonate his vehicle.

Two bystanders also died in the assault in Baqouba, the scene of fierce fighting last week between American soldiers and insurgents who tried to seize government buildings and police stations.

Saboteurs also blew up part of a strategic crude oil pipeline that runs from the country's northern oil fields to the south, police officials said. Fire crews and police from at least three nearby cities worked into the night to extinguish the blaze near Musayyib, about 50 miles southwest of Baghdad. Pipelines in that area have been hit several times in the past few weeks.

Between Baghdad and the restive city of Fallujah, insurgents fired rocket-propelled grenades and automatic weapons at a U.S. convoy of 20 gasoline tankers. There were no reports of casualties.

In Kirkuk, U.S. and Iraqi forces detained six members of a militant group suspected of a string of assassinations in the north. The men were believed to be members of Ansar al-Islam (search), a Kurdish group believed linked to Al Qaeda, said Iraqi police Col. Sarhat Qader.

Although Iraq regained sovereignty last Monday, about 160,000 foreign troops, most of them Americans, remain here under a U.N. resolution to help the new government restore security.

On Sunday, Allawi rejected troop offers from Jordan's King Abdullah II, telling ABC's "This Week" that "we are not asking" for additional soldiers.

The Iraqis are not eager to bring in Arab troops — especially from neighboring countries - fearing it could complicate relations with Syria and Iran, which U.S. and Iraqi officials have alleged have not done enough to control infiltration across their borders.

The Associated Press contributed to this report.