A truck bomb ripped through a line of cars at a checkpoint in Fallujah as bombings and shootings across Iraq Friday killed at least 20 people, including a U.S. Marine. President Jalal Talabani ordered the new parliament to hold its first session later this month.

The U.S. military identified the five killed in the Fallujah attack as a U.S. Marine, three members of an Iraqi family and an Iraqi soldier.

Car bombs also killed three people in Samarra, where an attack on a Shiite shrine last month ignited nearly two weeks of sectarian violence that raised fears of civil war.

Authorities in Baghdad and south of the capital discovered the bodies of eight more men — many of them blindfolded, handcuffed and shot in the back of the head.

The unrelenting violence has complicated negotiations to form a broad-based government after Dec. 15 parliamentary elections.

Talabani's chief of staff told The Associated Press that the president had ordered parliament to meet later this month.

"The president of the republic has called for parliament to hold its first session on March 19," Kamran al-Karadaghi said.

Despite the decree, there still was no resolution of the bitter dispute over a new term for Shiite Prime Minister Ibrahim al-Jaafari, prompting Massoud Barzani, the president of the Kurdish region of Iraq, to issue a statement saying the country was in political "crisis."

Barzani invited the leaders of all the major blocs in parliament to meet with him in the northern city of Irbil as soon as possible to seek a resolution.

The president has challenged al-Jaafari's candidacy on grounds he is too divisive and would be unable to form a government representing all Iraq's religious and ethnic factions. There was also great unease over al-Jaafari's close ties to radical anti-American cleric Muqtada al-Sadr.

U.S. Ambassador Zalmay Khalilzad also hoped to coax the country's major politicians to join him at a conference, Time magazine reported on its Web site. Elizabeth Colton, U.S. Embassy spokeswoman in Baghdad, said Friday that no meeting had been set.

The United States wants to leave behind a strong central authority and has made that a precondition for its hopes to begin drawing down American forces this summer.

The opening of parliament is the first step in the process of forming Iraq's first permanent, post-invasion government. When parliament convenes, it has 60 days to accomplish the task.

The bomb exploded in Fallujah as large numbers of cars were waiting to pass through the security checkpoint going into the city, 40 miles west of Baghdad, police said. Five people also were wounded, including two policemen, police Lt. Mohammed Taha said.

"Today, Iraqi security forces were working alongside U.S. Marines to ensure the safety of the citizens of Fallujah," Marine spokesman Lt. Col. Bryan F. Salas said in a statement. "Our thoughts are with the families and friends of the individuals who lost their lives."

It was the first Friday that Baghdad was not under an extended curfew or vehicle restrictions since the shrine bombing in Samarra, and large numbers attended Mosque for the most important prayer service of the week without major incident.

In Samarra, where a Feb. 22 bombing of a Shiite shrine ignited reprisal attacks against Sunnis and other violence that killed about 500 people, one car bomb targeted police but killed a civilian. The other bomb, near the Sunni Qiba mosque, killed the imam and another person in the mostly Sunni city, 60 miles north of Baghdad. Five people were wounded in the attacks.

Elsewhere, a roadside bomb exploded as a police patrol was driving through west Baghdad, killing two officers and wounding four, police said.

Another bomb hit a U.S. tank in east Baghdad, setting it afire and blowing off the treads, police said. The American military said the M1A2 Abrams tank hit a roadside bomb and the crew escaped unharmed.

Six of the bodies — between the ages of 30 and 45 — were found in two suburbs east of Baghdad and non bore identification, police said.

The bodies of two more bullet-riddled men — one of whom also had his throat slit — were brought to the morgue in Kut, 100 miles southeast of Baghdad, officials said.

South of the capital, a roadside bomb killed a 10-year-old boy and wounded his 8-year-old friend as they played in Amarah, police said. Police defused to other bombs at the scene.

A policeman in Tikrit died disarming a roadside bomb when a second explosive device detonated, also wounding two others.