A car bomb exploded Saturday in central Iraq, killing five people, including four police officers on patrol, while gunmen killed an education official in Baghdad (search). A U.S. Marine was killed in Ramadi, the military said Saturday.

The car bomb in Khan Bani Saad (search), near the troubled city of Baqouba in central Iraq, also injured two police officers and three civilians, provincial police Col. Mudafar al-Jubori said.

In Baghdad, gunmen opened fire from a car, killing Hassib Zamil outside of the Education Ministry offices in the Sadr City (search) neighborhood, education official Ibrahim Abid Wali said.

The Marine was killed Friday while conducting security operations in Ramadi, the U.S. military said.

In the capital Friday, insurgents fired a rocket propelled grenade and shot at an armored vehicle used to transport U.S. troops on a road leading to the dangerous airport highway, injuring two American soldiers, the U.S. military said.

As of Friday, at least 1,532 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Jostling for parliamentary leadership positions intensified Saturday, one day before the newly elected National Assembly holds its third meeting.

Adnan Pachachi (search), a senior Sunni assembly member, nominated himself for one of two vice presidential posts expected to be filled by a Sunni Arab.

Lawmakers remained divided over Sunni Arab candidates for parliamentary speaker.

In Tikrit, thousands assembled in a stadium to support Sunni Arab legislator Meshaan al-Jubouri's candidacy for speaker.

A group of Sunni leaders nominated al-Jubouri on Wednesday, but it wasn't clear if he had the backing of the entire Sunni community. Lawmakers in other coalitions also voiced their opposition to his candidacy.

Grand Ayatollah Ali al-Sistani, the most revered Shiite cleric in Iraq, recently told a Shiite lawmaker, Dhari al-Faiadh, that the assembly members should select a speaker "in a democratic way," said Maithen Faisal, an official in al-Sistani's Najaf office.

Last month, the reclusive cleric told a top U.N. official that he did not intend to involve himself in any political process, except for expressing his opinion during crises. The Shiite-led coalition in parliament came together under al-Sistani's guidance.

The U.S. military, meanwhile, praised an edict issued by Sunni clerics that called for Iraqis to join police and army forces, saying it was a sign that people were fed up with the insurgency. But the statement added that enlistees "must be prepared to serve all the people."

The edict, read by a cleric in the influential Association of Muslim Scholars, instructed enlistees to refrain from helping foreign troops against their own countrymen and said the move was designed to prevent security forces from falling into "the hands of those who have caused chaos, destruction and violated the sanctities."

The announcement, endorsed by a group of 64 Sunni clerics and scholars, could help the government boost the image of security forces struggling to fight the insurgency. For months, Sunni clerics had warned minority Sunnis, who were dominant under Saddam, against cooperating with Iraqi police and soldiers.