Sudan will close its embassy in Baghdad in an effort to win the release of six kidnapped employees, a Sudanese diplomat said Friday, a day after Al Qaeda in Iraq threatened to kill the captives if the diplomatic mission remained.

In Baghdad, long lines formed at gas stations as word spread that Iraq's largest oil refinery had shut down in the face of threats against truck drivers, and fears grew of a gas shortage.

Also in the capital, at least 15 people were killed in violence, including nine people sitting along the banks of the Tigris river who died in a drive-by shooting, police said. In separate attacks in Baghdad, a car bomber blew himself up next to a police patrol in a commercial area, killing three Iraqi civilians, and a mortar landed in a market, killing another three civilians.

Al Qaeda in Iraq, which has kidnapped and killed a string of Arab diplomats and embassy employees in a campaign to scare Arab governments from setting up full diplomatic missions in Iraq, had set a Saturday deadline for Sudan to "announce clearly that it is cutting its relations" with the Iraqi government, or it would kill five Sudanese hostages.

The Sudanese Foreign Ministry reported on Dec. 24 that six of its embassy employees were kidnapped, including the mission's second secretary. It was not immediately clear if the Al Qaeda statement referred to the same group.

"A statement was issued by the Sudanese government to close the embassy in Iraq to win the release of our kidnapped citizens," the embassy's charge d'affairs, Mohamed Ahmed Khalil, told The Associated Press.

The Qatari-based Al-Jazeera satellite channel on Thursday aired video showing the five kidnapped Sudanese sitting on chairs, talking to the camera, but no audio was heard. The channel said it received the video from the kidnappers.

Al Qaeda's statement said if Sudan did not close its embassy, "this government will bear the responsibility of presenting their diplomats as sacrifices."

The terror group said it had previously warned Arab nations of its "war against what is called the diplomatic missions in Baghdad," adding that the governments had ignored it, "still getting closer to the infidel Crusaders and Jews."

In July, Al Qaeda abducted the top Egyptian envoy in Baghdad and two Algerian diplomats. It later announced they had been killed. The group also snatched two Moroccan embassy employees in June and said that it had sentenced them to death, though it never stated whether it carried out the sentences.

The abduction of the Lebanese engineer came as another Lebanese kidnapped in Iraq was released. The Lebanese Foreign Ministry said Assad Hussein Younis was freed by his captors but it gave no details.

An international team, meanwhile, agreed on Thursday to assess Iraq's parliamentary elections, a decision lauded by Sunni Arab and secular Shiite groups who have staged repeated protests around Iraq complaining of widespread fraud and intimidation. They will arrive Monday, said Reem Arshad, an Iraqi elections official.

The Shiite religious bloc leading after the Dec. 15 poll also welcomed the decision and said it would help end any doubts about the elections.

"The number of votes our ticket has got are real and the coming team will give credibility to this number," said Ali al-Adib, a leading member of the conservative Dawa party that is a main member of the Shiite United Iraqi Alliance.

Reflecting efforts to quell ongoing friction among the ethnic factions, U.S. troops in Baghdad are beginning to focus more on training the Shiite-dominated special police forces in Iraq, Maj. Gen. William G. Webster Jr., commander of coalition forces in Baghdad, said Friday.

Webster also acknowledged that Iraqi detention facilities under the control of Iraq's Interior Ministry are still overcrowded, and the detainees, who are largely Sunni Arabs, show signs of injuries from past abuse. But he said inspections show no signs of recent abuse.

The decision announced Thursday by the International Mission for Iraqi Elections to send a team of assessors should help address opposition complaints of ballot box rigging and mollify those groups who felt their views were not being heard, especially among hardline Sunni Arab parties.

"It is important that the Iraqi people have confidence in the election results and that the voting process, including the process for vote counting, is free and fair," U.S. Ambassador Zalmay Khalilzad said.

There have been about 1,500 complaints lodged against the elections, including about 50 serious enough to alter the results in some districts. The overall result, however, was not expected to change.

It was unclear if the review would further delay the release of final results, now expected in early January.

An elections crisis could set back hopes for a broad-based government that would include minority Sunni Arabs as well as secular Shiites. Such a government could have the legitimacy necessary to diminish the insurgency — a key part of any U.S. military exit strategy.

The presence of two Arab experts on the International Mission for Iraqi Elections team could go far in helping to convince Iraqis that the review of the vote will be fair. The team will also consist of a Canadian and a European.

Preliminary results from the vote have given the governing United Iraqi Alliance a big lead — but one that would require forming a coalition with other groups.

Adding to the general uncertainty was the Dec. 18 shutdown of the refinery in Beiji. Minister of Oil Ibrahim Bahar el-Ulom told The Associated Press the facility "is considered one of the vital refineries in Iraq" and produces about 2 million gallons of gas a day.

As word of the shutdown spread, several hundred cars waited at one of Baghdad's biggest gas station.

"I left my work early, and I don't think I will have the opportunity to return to work today because of this long line," said Ahmed Khalaf, 33.