An alleged Al Qaida militant was executed for his role in one of Iraq's first and bloodiest bombings, a 2003 blast that killed a Shiite leader and 84 other people, a Justice Ministry official said Friday.

Oras Mohammed Abdul-Aziz was hanged Tuesday in Baghdad after being sentenced to death in October, Ministry Undersecretary Busho Ibrahim told The Associated Press.

The execution announcement was the first word that a suspect had been tried in the killing of Ayatollah Mohammed Baqir al-Hakim.

Al Qaida in Iraq claimed responsibility for the attack — a huge car bomb in August 2003 that went off outside the Shrine of Ali in Najaf, one of Shiite Islam's holiest sites, and killed al-Hakim.

Al-Hakim was the leader of the Supreme Council for the Islamic Revolution in Iraq and was poised to become a major figure in Iraqi politics following the fall of Saddam Hussein only months before his assassination. His brother, Abdul-Aziz al-Hakim, now heads the group, the largest Shiite party in parliament.

Ibrahim said Abdul-Aziz, from the northern city of Mosul, was affiliated with Al Qaida in Iraq and confessed to other attacks, including the 2004 killing of Abdel-Zahraa Othman, the president of the Governing Council, the U.S.-appointed body that ran Iraq following Saddam's fall.

The al-Hakim slaying was one of the first major bombings in Iraq and foreshadowed the four-year insurgency that followed. It came 10 days after the bombing of the U.N. headquarters in Baghdad killed 23 people, including the top U.N. envoy to Iraq, Sergio Vieira de Mello, an attack also claimed by Al Qaida in Iraq.

Also Friday, the military said a U.S. soldier died of wounds sustained in combat Thursday in western Baghdad.

With his death, at least 3,592 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count. The figure includes seven military civilians.

Meanwhile, differences have emerged among the three main Sunni groups forming the Iraqi Accordance Front, threatening to break up the alliance.

The disagreements surfaced Thursday after the front elected Ayad al-Samarraie as the chairman of the 44-member bloc in parliament. Until then, politician Adnan al-Dulaimi headed the front's faction in parliament.

Members of al-Dulaimi's Congress of the People of Iraq were angered after Iraqi media and Web sites reported that al-Samarraie, a member of the moderate Iraqi Islamic Party, was elected as the head of the front. Some of al-Dulaimi's followers called for a meeting to remove the Iraqi Islamic Party from the front.

Al-Dulaimi said he learned about al-Samarraie's election from the media, adding that what happened "took place without my knowledge, but this does not bother me."

"There was no coup to remove me and replace me by Mr. Ayad al-Samarraie," al-Dulaimi told Sharqiya television. "I am still the leader of the Iraqi Accordance Front ... and all what was reported in media is not accurate and not true."

Later Friday, Khalaf al-Ilyan, head of the National Dialogue Council which is the third group of the Iraqi Accordance Front, told Sharqiya that "the head of the parliamentary bloc is Dr. Adnan al-Dulaimi and any other measure has nothing to do with the front."

"We don't approve that," al-Ilyan said, referring to the election of al-Samarraie. "We call upon the brothers, members of the front, to abide by the rules of the front and what its leaders decide. Any other measure will be considered null."

The Iraqi Islamic Party is considered the backbone of the Iraqi Accordance Front, holding 27 of its parliament seats. Iraqi Islamic Party leader Tariq al-Hashemi is Iraq's Sunni vice president.

Members of the Iraqi Accordance Front are variously boycotting Cabinet meetings and parliament meetings in response to what they claim are two major efforts to sideline them: an arrest warrant issued against the Sunni culture minister accused of masterminding an assassination attempt two years ago and a parliamentary vote demanding the resignation of the Sunni speaker.

Kurdish and Shiite leaders have been urging Sunni legislators and Cabinet ministers to end their boycott, saying their presence in parliament is urgently needed as it prepares to begin discussing the key draft oil law.

Al-Maliki has struggled to get his coalition behind the bill, part of a long-delayed political package that the Bush administration hopes will reconcile Iraq's Sunni Arab minority with the government, reduce support for the insurgency and ease violence.

The law aims to regulate Iraq's oil industry and will determine the central government's role, and companion legislation that is nearly finalized sets how oil wealth will be distributed among regions.