Three roadside bombs planted in succession struck a police convoy in one of Iraq's most dangerous provinces on Sunday, killing five policemen. In Baghdad, the leader of a Sunni group allied with the U.S. died when his booby-trapped car exploded.

The bombs planted along a main thoroughfare targeted a police convoy in Jalawla, 60 miles north of Baghdad, said Ibrahim Bajilan, head of the provincial council of Diyala.

The province, northeast of Baghdad and bordering Iran, remains a major security challenge for the U.S.-backed Iraqi government, even as violence drops in other parts of the country.

Diyala has had a volatile mix of Sunni and Shiite militants, and some Iraqi Arabs are concerned that forces from the Kurdish autonomous region in northern Iraq are encroaching on territory there.

On Saturday night, a bomb killed the leader of a U.S.-backed, Sunni armed group in the al-Furat neighborhood of western Baghdad.

The bomb exploded in the car of Fuad Ali Hussein, killing him as well as his deputy and two bodyguards. Hussein was head of a neighborhood awakening council — a term describing Sunni Arab insurgents and tribesmen who turned against al-Qaida in Iraq and formed alliances with the United States.

Hussein's death was confirmed by a police officer and the head of another awakening council. Both requested anonymity for security reasons. The U.S. military said it knew of one person killed and another wounded in that attack.

In political developments, Iraq's parliament voted to lift the immunity of a Sunni Arab lawmaker who visited Israel to attend a counterterrorism conference this month. Mithal al-Alusi was also barred from traveling outside Iraq or attending parliamentary sessions.

Osama al-Nujeifi, a Sunni Arab lawmaker, and Shiite lawmaker Haider al-Ibadi said al-Alusi's trip was illegal and a humiliation for Iraqis who see Israel as a historic enemy.

Also Sunday, Prime Minister Nouri al-Maliki formed a committee to investigate the killing of four employees of the Iraqi television network Al-Sharqiya as they filmed an episode on the Islamic holy month of Ramadan, which began two weeks ago.

The Iraqi government has repeatedly accused Al-Sharqiya of bias, sensationalism and spreading anti-government propaganda. Owned by a former chief of radio and television for Saddam Hussein, the station is seen by many Shiites as pro-Sunni.

The employees of the station were abducted and killed Saturday in the northern city of Mosul. They included the head of the station's office in Mosul, two cameramen and a driver.

Al-Maliki's office said in a statement that he had ordered security forces "to chase down the perpetrators and bring them to justice for punishment."

U.S. Ambassador Ryan Crocker also condemned the killings.

Brig. Khalid Abdul-Sattar, the police spokesman in Ninevah province, said 80 people were detained for questioning.

Before Saturday's attack, the New York-based Committee to Protect Journalists had reported that 132 journalists and 50 other media employees had been killed since the 2003 start of the Iraq war.

Also Sunday, an American soldier in Iraq died of causes unrelated to combat, the U.S. military said. The cause of death was under investigation.