Updated

A bomb exploded alongside a group of Iraqi men waiting for work in eastern Baghdad on Wednesday, killing at least eight and wounding more than 50, as a new video from kidnappers threatened to kill two German hostages if Germany fails to stop cooperating with the Iraqi government.

Witnesses said a man placed a bag full of explosives near a cart that sold tea to the workers as they waited for daily construction jobs, said Col. Ahmed Abboud, chief of police in the New Baghdad area where the explosion occurred.

"The people did not suspect him when he first came with the bag because all workers carry their food in bags," Abboud told The Associated Press.

The attack happened around 7 a.m. at an intersection crowded with bystanders near a Sunni Muslim mosque. Abboud and another police official, Capt. Mohammed Jassim Jaber, said at least eight people were killed and more than 50 wounded.

Also Wednesday, U.S. troops fired on an approaching Canadian Embassy convoy that failed to obey signals to stop in the heavily fortified Green Zone in Baghdad, but there were no injuries, said U.S. military spokesman Lt. Col. Barry Johnson. A Canadian Embassy spokeswoman in Jordan said four Canadian diplomats were in one of the vehicles, including the charge d'affairs.

In a series of apparent sectarian killings Tuesday, police found the bodies of 16 handcuffed and blindfolded young men around Baghdad, and gunmen shot dead the wife and two sons of a Sunni Arab cleric north of the capital. A roadside bomb also killed a British soldier in southern Iraq.

Kidnappers threatened to kill Thomas Nitzschke and Rene Braeunlich if Germany does not close its embassy in Iraq, withdraw all the German companies from Iraq and stop cooperating with the Iraqi government within three days.

The videotape aired on Al-Jazeera television showed Braeunlich speaking and clasping his hands in front of him as if begging. No audio was heard.

The two men were abducted last week in the northern industrial city of Beiji.

The video came a day after Jill Carroll, a 28-year-old freelancer for the Christian Science Monitor also held hostage, appeared veiled and weeping in footage on Al-Jazeera. U.S. officials said they have ruled out meeting the kidnappers' demand to release all Iraqi women in detention.

"Everything is being done to work with those who might have influence, and there are an awful lot of people who are calling for her release," U.S. Secretary of State Condoleezza Rice said Tuesday.

More than 250 foreigners have been taken captive since the war started and at least 39 have been killed.

Reporters Without Borders, an international journalist advocacy group, said it would send representatives to the Middle East to promote a campaign in the Arab media for the release of Carroll, who was seized in Baghdad on Jan. 7.

The father of a kidnapped Canadian Christian activist urged the release of his son and three colleagues.

"I appeal for the captives of my son and his three friends to release them unharmed," Dalip Singh Sooden said on Al-Jazeera Tuesday. His son, 32-year-old Harmeet Singh Sooden, was seized Nov. 26 in Baghdad.

British Cpl. Gordon Alexander Pritchard, 31, was killed Tuesday as he led a three-vehicle convoy hit by a roadside bomb in Umm Qasr, near the border with Kuwait.

He was the second British soldier killed in Iraq in as many days, making his death the 100th British military fatality since the conflict began in March 2003.

The 8,000-strong British contingent is based in the Shiite south, which is less violent than the Sunni Arab areas to the north where most of the 136,000 U.S. troops operate.

Two children died during a clash between U.S. troops and insurgents in the western town of Hit, U.S. Marine spokesman Capt. Jeffrey Pool said.

Two other Iraqis were shot and killed when they violated orders for residents to stay in their homes during raids by paramilitary troops backed by U.S. forces in Samarra, 60 miles north of Baghdad, police said.

Three Iraqi soldiers were killed and six wounded in a gunbattle in Buhriz, a tense Sunni Arab town 30 miles northeast of Baghdad.

In the volatile western Baghdad neighborhood of Ghazaliyah, 11 bodies were discovered in a truck, all shot in the head, police added. Five men's bodies were also found near a sewage plant in the eastern Rustamiyah district where sectarian death squads often leave corpses. It was not known if they were Sunni Arabs or Shiites.

Sunni Arab and Shiites extremists have been carrying out reprisal killings that have claimed hundreds of lives and sharpened sectarian tensions as Iraqi politicians try to form a new government after Dec. 15 national elections. The killings come at a time when U.S. officials are pushing the Iraqis to include more Sunni Arabs, who form the backbone of the insurgency.

In what appeared to be a continuation of the killings, gunmen shot dead the wife and two sons of the Sunni Arab cleric Qassim Daham al-Hamdani Monday night in Muqdadiyah, about 60 miles north of Baghdad, police said. The cleric was not home.

Japan's Kyodo News agency said Tokyo will begin withdrawing troops from Iraq in March and complete the pullout by May, ending its largest military mission since World War II. Japanese Foreign Minister Taro Aso denied the report, saying no specific timetable had been discussed.

Kyodo said an agreement on the timetable had been reached during a secret meeting among officials from Australia, Britain, Japan and the United States.

A spokesman for Britain's Ministry of Defense said he was unaware of such a meeting but that London speaks to its coalition partners frequently.

Iraq's national security adviser, Mouwafak al-Rubaie, said he believed U.S. troop strength would fall below 100,000 by the end of the year and most U.S. and foreign forces would leave Iraq sometime next year. U.S. officials dismissed the forecast as speculation.

The Pentagon has trimmed troop strength from a high of 160,000 to about 136,000 after last month's election.