BAGHDAD, Iraq — A suicide car bomber targeted police recruits riding in a bus north of Baghdad today, killing seven people, and gunmen in the capital killed five laborers, police said.

At least three police recruits were killed by the car bomb, and another four people also died, although officials couldn't immediately say whether they were police recruits or civilians. Thirteen people were wounded, the Diyala police said. The bus had been traveling to a training center in Baqouba, 35 miles northeast of Baghdad.

In the capital, gunmen in two cars opened fire on laborers, killing five, police Capt. Qasim Hussein said.

Elsewhere, a 7-ton truck slammed into a bus carrying civilian contractors on a U.S. air base in the western Anbar region Sunday, the U.S. military said today. Four American civilian contractors were killed, and 18 civilians were injured, including eight who were flown by medical helicopter to Baghdad.

The cause of the accident was under investigation. No hostile action was involved, the military said.

In other violence, a car bomb exploded in Baghdad near an American convoy, Hussein said. Police had no information on casualties, and U.S. officials do not usually comment on such attacks.

Fuel resumed flowing at Iraq's largest oil refinery, ending a nearly two-week hiatus caused by deteriorating security. The shutdown forced stations around the country to ration gas, creating long lines.

"We started (Sunday) to supply the tankers with oil products after the government promised to secure them along the highways," Ahmed Ibrahim Hamadi said today.

Prime Minister Ibrahim al-Jaafari and the ministers of defense and education were welcomed by President Jalal Talabani, a Kurd, in Sulaimaniyah, 160 miles northeast of Baghdad, today.

Al-Jaafari is a leading member of the United Iraqi Alliance, a religious coalition of majority Shiites that won the most votes in the Dec. 15 parliamentary elections, according to preliminary results.

Sunni Arabs made their opening bid Sunday in what could be protracted negotiations to form a new government. Leaders of the minority's main political group, the Iraqi Accordance Front, traveled to the northern city of Irbil for a meeting today with the president of the Kurdish region, Mazoud Barzani.

On Sunday Barzani met with al-Jaafari and agreed on "essential principles for exerting efforts to form a broad-based government," Barzani said.

Preliminary results from the elections have given the Shiite group a strong lead in the voting for Iraq's 275-member parliament, but not enough for it to govern without other political blocs. Final results are expected as early as this week.

A year ago, it took nearly three months of negotiations between the Shiite religious alliance and a coalition of Kurdish parties to form an interim government after a Jan. 30 election that was boycotted by the Sunni Arabs at the core of the insurgency.

The first three months of 2006 look more crucial as Iraq tries to shape an administration that will govern for four years. U.S. officials are pushing the parties to form a broad-based coalition government, and failed negotiations could worsen the civil strife.

The Irbil meetings came ahead of today's visit to Iraq by a team of international monitors who will assess the elections. The United Nations has called the polls credible, but opposition groups have denounced them as rigged.