Updated

Assailants gunned down the chief of Saddam Hussein's (search) tribe in the ousted leader's hometown of Tikrit a few weeks after he publicly disavowed Saddam. Although the motive was unclear, Abdullah Mahmoud al-Khattab had many enemies, the regional governor said Tuesday.

Elsewhere in Iraq , two attacks against American forces wounded at least six soldiers, U.S. troops shot and killed four people at checkpoints and a mosque explosion killed 10 people in Fallujah — further stirring anti-American sentiment in a town where Saddam and his Baath Party still enjoy support.

In Baghdad, the top U.S. official in Iraq, L. Paul Bremer (search), said the U.S.-led provisional authority was "well on track to establish an Iraqi interim administration by mid-July." The United States has pledged to set up a political council of 25 to 30 Iraqis that will appoint heads of ministries and be consulted on major decisions taken by the occupation government.

Bremer also said the U.S.-led authority has asked airlines to submit applications to resume commercial service to Baghdad (search).

"Day by day, conditions in Iraq continue to improve," said Bremer. "Freedom becomes more and more entrenched and the dark days of the Baathist regime are further and further back in people's memories."

Despite his reassurances, a burgeoning insurgency has seen several attacks on U.S. troops every day, leading some to worry about the possibility of a Vietnam-style political and military quagmire.

In Washington, President Bush said Tuesday that anti-American violence was expected, because Saddam loyalists will stop at nothing to regain power.

"These groups believe they have found an opportunity to harm America, to shake our resolve in the war on terror, and to cause us to leave Iraq before freedom is fully established," Bush said. "They are wrong and they will not succeed."

"There will be no return to tyranny in Iraq," he said.

In Tikrit, Abdullah Mahmoud al-Khattab (search), who was leader of Saddam's Bani al-Nasiri (search) tribe, was shot and killed Sunday afternoon while he rode in his car.

Governor Hussein al-Jubouri said al-Khattab's son, Odai, also was wounded when assailants fired from a pickup truck and fled the scene.

The killing highlighted the shifting alliances that have characterized Iraq as the country emerges from 35 years of brutal, one-man rule. Even those eager to distance themselves from Saddam often pay dearly for their past links to him.

Al-Khattab "had many enemies and he had confiscated a lot of properties and killed many people," the governor said, adding, "The person who killed him could have taken revenge."

Several Tikrit residents said the killers could have been Saddam loyalists angered at the tribal leader's public disavowal of the ousted dictator.

Saddam still enjoys a degree of popularity in Tikrit, where he built roads and schools and soccer fields. Wall graffiti here reads, "Pray for Saddam's victory because he's a genuine Iraqi" and "May the occupation fall and may Saddam return."

"He's just, he's pious, he's a real Muslim, he loves his people," said Tikrit resident Abu Ahmed at the mention of Saddam's name.

Most other Iraqis express disdain for Saddam, yet anti-U.S. forces have persisted in stepping up attacks on occupation forces in recent days.

On Tuesday, assailants traveling in a vehicle in central Baghdad fired a rocket-propelled grenade at a U.S. military vehicle, wounding three soldiers. Another grenade slammed into a U.S. truck on a road 12 miles south of Baghdad, injuring three soldiers.

In western Baghdad, U.S. troops shot and killed two people when their car didn't stop at a checkpoint, witnesses said. A U.S. military spokesman said he had heard about the incident but could not confirm it. Later, two civilians were shot and killed at another checkpoint, one by soldiers who feared he was an insurgent and another by a stray bullet, witnesses said.

The increasing attacks have killed more than 22 U.S. soldiers and wounded dozens more since major combat was declared over on May 1, and many troops have become quicker to pull their guns.

A U.S. sweep dubbed Operation Sidewinder (search) moved against insurgents in the so-called "Sunni triangle" north and east of Baghdad for a third day Tuesday. The Army's 4th Infantry Division conducted 25 raids and detained 25 suspects, a military statement said. No major fugitives of Saddam's regime were among them.

In Fallujah, a blast in a cinderblock building in the courtyard the al-Hassan mosque killed 10 Iraqis and wounded four late Monday, said Col. Guy Shields, spokesman for the U.S. military in Baghdad. Iraqis insisted the blast was caused by a U.S. missile — an account the military denied.

After the explosion, dozens of people gathered around the site shouting anti-American slogans.

"There is no God but Allah, America is the enemy of God," they chanted, as a crane lifted pieces of concrete.

Fallujah, 35 miles west of Baghdad, has been a hotbed of anti-American activity and scene of several confrontations involving U.S. troops.

Meanwhile, a weekend explosion at an ammunitions depot killed at least 15 people and injured at least four near Hadithah, 150 miles northwest of Baghdad, officials said Tuesday.

Metal scavengers dismantled 155 mm artillery rounds, spreading gunpowder on the ground at the depot that housed old Iraqi artillery. A spark there Saturday triggered the blast, local officials said.

Policeman Lt. Saad Aziz said there was a large pile of TNT at the depot, and people were smoking. "This kind of TNT is very sensitive to heat. A small spark could set the whole thing off," he said.

Mohammed Nayil Assaf, Hadithah's mayor, put the death toll at 25 and the injured at 6. He insisted that U.S. troops failed to adequately protect a large amount of ammunition stored in the area.

"It was a tragic day for Hadithah," he told the Associated Press outside the town hall, near a 3-foot-high pile of shell casings seized from looters.