Shiite gunmen raided an Iraqi police station in the holy city of Najaf and held it for two hours Thursday in the first outbreak of fighting since an agreement to end weeks of clashes between U.S. troops and militia forces. Six Iraqis were killed and 29 were injured, including eight children, hospital officials said.

The interim prime minister sought to shore up internal political support by promising to honor the interim constitution as authorities prepare for the handover of power from the U.S.-led coalition.

Also Thursday, gunmen claiming to belong to a militant Islamic group displayed four Turks they said were kidnapped in Iraq, demanding that Turkish companies end all business here and pull staff out of the country.

Chaos swept the southern city of Najaf after gunmen loyal to radical cleric Muqtada al-Sadr (search) overran the Ghari police station after a 10-hour gunbattle, witnesses said. The station, located 250 yards from the Imam Ali Shrine (search), was looted and police cars were burned.

"We sent a quick reaction unit to assist the policemen defending the station, but they were overwhelmed by al-Sadr fighters," said Najaf Gov. Adnan al-Zurufi. "We will solve this problem as soon as possible. We will ask for the help of the Americans, if necessary."

Hours later, al-Sadr's forces withdrew, and rioters looted the damaged cars.

Later Thursday, Iraqi police traded gunfire with al-Sadr's militia near one of the radical Shiite cleric's houses, said Muhanad Kadhin, a police official. Police went to the nearby al-Hakim hospital after reports that wounded policemen brought there were threatened by al-Sadr fighters.

Kadhin said the militiamen started firing first, prompting police to fire back. No injuries were reported.

Fighting ebbed around the main police station, which came under fire Wednesday night when the attacks began.

U.S. forces were not involved in the clashes, and it was unclear whether the violence marked the end of the cease-fire in Najaf, mediated by Shiite leaders and al-Sadr's militia, or resulted from police attempts to crack down on petty crime in the city.

Police and witnesses said trouble began when authorities tried to arrest suspected thieves at the bus station near police headquarters. Masked attackers responded with machine gun fire and rocket-propelled grenades near the headquarters building.

One gunman was killed when police returned fire, al-Sadr's spokesman Qais al-Khazali said. The slain man's armed relatives attacked the headquarters Thursday in revenge, he said. Fighting later moved to the second station.

"We are trying to convince them to stop shooting," al-Khazali said. "We are still committed to the truce."

Last week, al-Sadr agreed to send his fighters home and pull back from the Islamic shrines in Najaf and its twin city of Kufa, handing over security to Iraqi police. The U.S. Army also agreed to stay away from the holy sites to give Iraqi security forces a chance to end the standoff.

The clashes illustrate the chaotic situation in Iraq as the U.S. military begins phasing down its operations ahead of the June 30 transfer of sovereignty.

One senior U.S. military official, speaking on condition of anonymity, said coalition forces would not leave the streets immediately after June 30 but would phase down their presence as Iraqi security troops gradually take control.

Iraq's interim authorities took steps Thursday to reassure Kurdish members of their government, who have threatened to walk out because the U.N. Security Council resolution on sovereignty failed to include an endorsement of the interim constitution — known as the Transitional Administrative Law.

Prime Minister Iyad Allawi's (search) spokesman, Gorgues Hermez Sada, said the government intended to honor the interim constitution while Iraq makes the transition to elections, which are expected next year.

The Kurds fear they will be sidelined politically by the Shiite Arab majority, despite assurances from Allawi and others that the new government would stick by its commitments for communal rights.

U.N. diplomats said the decision was made to keep a reference to the interim constitution — the Transitional Administrative Law — out of the resolution to appease Iraq's most influential Shiite cleric, Grand Ayatollah Ali al-Husseini al-Sistani (search), who grudgingly accepted the charter when it was approved in March.

Allawi also directed his attention to domestic anger at continuing power outages in the transition period, appealing to the public to be vigilant against attacks on oil pipelines and electrical grids. He charged that foreign fighters had targeted Iraq's infrastructure, but offered no evidence to support the claim.

Allawi said saboteurs had made 130 attacks on oil pipelines in the last seven months and that more than $200 million has been "stolen out of the pockets," of Iraqis.

"These saboteurs are not freedom fighters. They are terrorists and foreign fighters opposed to our very survival as a free state," he said. "Anyone involved in these attacks is nothing more than a traitor to the cause of Iraq's freedom and the freedom of its people."

Allawi's comments follow a series of attacks against infrastructure targets — trying to shake public confidence as a new Iraqi government prepares to take power.

Coalition authorities have said guaranteeing adequate electricity is a benchmark of success in restoring normalcy, but the crumbling infrastructure and sabotage have hampered efforts, especially in Baghdad.