BAGHDAD, Iraq (AP) _ Militants threatened to decapitate two Americans and a Briton being held hostage unless their demands were met within 48 hours, and in northern Iraq a car bomb killed at least 21 people and wounded 67 on Saturday.
The threat came in a video purportedly from a militant group linked to al-Qaida that showed Americans Jack Hensley and Eugene Armstrong and Briton Kenneth Bigley, the first word of their fate since the three construction workers were abducted from their Baghdad office two days ago.
Kidnappings and spectacular bombings have become the signature weapons of insurgents waging a 17-month campaign to force the United States and its allies to pull out of Iraq and undermine the interim government of Prime Minister Ayad Allawi.
The car bombing in Kirkuk was the third this week targeting Iraq's beleaguered security forces, seen by insurgents as collaborators with U.S. troops and their allies.
In the hostage video, posted on an Web site known for its Islamic militant content, kidnappers purporting to belong to Tawhid and Jihad _ a group led by Jordanian militant Abu Musab al-Zarqawi _ demanded that Iraqi women detained at two American-controlled prisons here are freed within 48 hours or the captives will be beheaded. A U.S. military official said two women are in U.S. custody.
The footage showed the three hostages sitting on the floor, blindfolded but apparently unharmed. Each identified himself and said,``My job consists of installing and furnishing camps at Taji base,'' referring to a U.S. base 15 miles north of Baghdad.
At one point, the rifle of an armed militant pointed down at the head of the man who identified himself as Hensley.
``God's soldiers from Tawhid and Jihad were able to abduct three infidels of God's enemies in Baghdad,'' said a masked militant dressed in black, standing behind the men as he read from a statement.
``They offer logistic support to American troops in Iraq, as was shown from investigation and the documents seized with them,'' he said.
If their demand is not met, the speaker warned, ``by the name of God, these three hostages will get nothing from us except their throats slit and necks chopped, so they will serve as an example.''
U.S. Embassy officials were not immediately available to comment. A British diplomat in Baghdad said the embassy was aware of the tape but would not comment. The men's employer, Gulf Supplies and Commercial Services, refused to comment when contacted by The Associated Press.
The masked man in the video accused Iraq's interim president of enabling ``infidel foreigners'' to ``violate the honor of Muslim women, humiliate people and suck up the riches of the country.''
The group demanded the release of women being held at Abu Ghraib and Umm Qasr prisons.
Lt. Col. Barry Johnson, a U.S. military spokesman in Baghdad, said coalition forces do not hold any women at Abu Ghraib or at Camp Bucca, a U.S. detention facility near Umm Qasr.
``The only females we hold are two high-value detainees, which are kept with the other approximately 100 high-value detainees in a separate, secure location,'' Johnson said.
Both facilities are run by American forces. Umm Qasr is in British-controlled southern Iraq, and Abu Ghraib is a prison near Baghdad that was the scene of a scandal involving U.S. soldiers sexually humiliating male prisoners. Fears about the safety of women inmates have multiplied since then.
He did not rule out the possibility that women were among an estimated 1,500 prisoners held at an Iraqi facility for convicted criminals at Umm Qasr.
Nouri Abdul Raheem, an official at the Justice Ministry, said a U.S.-Iraqi committee reviewing the cases of detainees had decided to release all women and juveniles within the next two weeks.
More than 100 foreigners have been kidnapped in Iraq, and many have been executed. At least five other Westerners are being held hostage in Iraq, including an Iraqi-American man, two female Italian aid workers and two French reporters.
The video surfaced as attackers set off car bombs in Baghdad and Kirkuk, where Health Ministry officials said at least 21 people were killed and 67 wounded.
In Kirkuk, a car sped across an open field toward a crowd waiting to apply for jobs with the Iraqi National Guard, witnesses said.
Guardsmen opened fire before the car blew up, said Maj. Thomas Williams, a spokesman for the Army's 2nd Brigade, 25th Infantry Division.
``There was a huge explosion and a big fire,'' said Asu Ahmed, a street vendor. ``There were many dead and injured people, and I helped put them in ambulances.''
The street outside the guard headquarters was littered with bloodied bodies, debris and shards of glass. Ambulances with sirens wailing rushed to scene, where firefighters doused the flames.
Initial reports indicated the victims were civilians and that no guardsmen were harmed, Williams said.
One of the job-seekers, Rustem Abdellah, 33, said the attack occurred as recruits were lining up to read the lists of those who had passed the physical fitness test. He suffered burns to his face and chest.
``I am a graduate from the oil institute,'' Abdellah said from his hospital bed. ``But there are no jobs available in the oil sector, and I was forced to join the guard force because of the difficult economic situation.''
The Iraqi National Guard is the centerpiece of U.S.-backed efforts to build a strong Iraqi security force capable of taking over security operations in many areas from American troops before planned January elections.
In Baghdad, a car bomb detonated near a bridge over the airport road, wounding three U.S. soldiers, the military said. Plumes of thick black smoke were seen rising from the scene as U.S. helicopters clattered overhead. The treacherous stretch of the road is the site of daily attacks against U.S. troops and their supply convoys.
The Americans insisted the militants' campaign of violence won't succeed.
``The continued targeting of Iraqi Security Forces shows the desperation of anti-Iraqi forces as they recognize the continued improvement and capability of the Iraqi National Guard and Iraqi Police,'' said Maj. Neal O'Brien of the Army's 1st Infantry Division.
In other developments:
_Hospital officials said residents on Friday found the body of Anbar province's deputy governor, Bassem Mohammed, who was kidnapped earlier this month. Anbar is a center of activity by Sunni insurgents.
_A roadside bomb exploded in a small side street in central Baghdad, killing one Iraqi man and seriously wounding two, police and witnesses said.
_British troops pulled out of the main office of radical Shiite cleric Muqtada al-Sadr in the southern city of Basra after occupying it and seizing a weapons cache there a day earlier amid fighting that killed three and wounded five.
_Mohammed Zibari, a senior official with Iraq's state-run North Oil Co., survived an assassination attempt when his convoy came under fire in the northeastern city of Mosul, police said. Five of his bodyguards were killed and four wounded.
_A mortar shell exploded near the entrance to the Technical Institute in Baqouba, north of Baghdad, wounding 11 students as they waited for the results of their final exams, police said.