The footage aired as attackers set off a series of explosions that killed at least 20 and wounded 81 nationwide, including a car bombing in Kirkuk, as insurgents stepped up a campaign to undermine the interim government of interim Prime Minister Ayad Allawi and force the United States and its allies to pull out of Iraq.
Separately, a militant group in Iraq claimed it is holding 10 hostages working for an American-Turkish company in a tape broadcast by the pan-Arab station Al-Jazeera Saturday.
Also, two car bomb attacks on the highway to Baghdad's international airport killed two American soldiers and wounded 11 on Saturday, the military said.
The first bomb exploded near an overpass on the road linking the capital to the airport as a convoy passed by, wounding three soldiers. Plumes of thick black smoke were seen rising from the scene and a U.S. helicopters clattered overhead.
At around 4 p.m., U.S. soldiers traveling to the scene of the first attack were hit by a second car bomb, killing two and wounding eight, the military said.
The treacherous stretch of road is the site of frequent attacks against U.S. troops and their supply convoys. In a travel warning issued Saturday, the U.S. State Department described the airport road as among the country's most dangerous.
In other developments Saturday:
The first tape, initially shown on the Arab satellite news station al-Jazeera and later on a Web site known for its Islamic militant content, was the first word on the fate of Americans Jack Hensley and Eugene Armstrong and Briton Kenneth Bigley. The authenticity of the tape could not be verified.
The three engineers were seized Thursday from their home in a leafy Baghdad neighborhood in a bold raid that shook the city's dwindling international community.
The men appeared unharmed, sitting on the floor with heads slightly bowed and white blindfolds covering their eyes. Each identified himself and repeated: "My job consists of installing and furnishing camps at Taji base."
At one point, a militant's rifle pointed down at the head of the man who identified himself as Hensley.
A masked militant dressed in black stood behind the men and read from a statement claiming to be from Tawhid and Jihad, the group led by key Jordanian terror suspect Abu Musab al-Zarqawi. The group's black banner was not visible behind the men as in previous videotapes.
"God's soldiers from Tawhid and Jihad were able to abduct three infidels of God's enemies in Baghdad - two Americans and a British," the masked militant said. "They offer logistic support to American troops in Iraq, as was shown from investigation and the documents seized with them."
He accused Allawi of enabling "infidel foreigners" to "violate the honor of Muslim women, humiliate people and suck up the riches of the country" and gave the United States and Britain 48 hours to release Iraqi women detained at Abu Ghraib and Umm Qasr prisons.
If the 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."
Both the named facilities are run by American forces. Umm Qasr is in British-controlled southern Iraq, and Abu Ghraib is a prison near Baghdad where U.S. soldiers were photographed sexually humiliating male prisoners. Fears about the safety of women inmates have multiplied since then.
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.
He did not rule out the possibility that women were among an estimated 1,500 prisoners at an Iraqi facility for convicted criminals at Umm Qasr.
But Justice Ministry official Nouri Abdul Raheem said a U.S.-Iraqi committee reviewing the cases of detainees had decided to release all women and juveniles within the next two weeks.
Gulf Supplies and Commercial Services, the employer of the kidnapped men, refused to comment on the tape when contacted by The Associated Press from Dubai, United Arab Emirates.
More than 100 foreigners have been kidnapped in Iraq, and many have been executed. At least five other Westerners are currently being held hostage here, including an Iraqi-American man, two female Italian aid workers and two French reporters.
Kidnappings and dramatic explosions have become insurgents' weapons of choice since the U.S.-led invasion in March 2003 that ousted Saddam Hussein.
The previously unknown group in the other tape at came to light Saturday called itself the "Salafist Brigades of Abu Bakr Al-Siddiq." It gave an ultimatum of three days for the company to leave Iraq or it will kill the 10 hostages, the station's presenter said.
The Al-Jazeera presenter said the station received a copy of the tape but did not say how. The group identified the company as an American-Turkish, operating in Iraq, but did not give a name.
The station only aired a clip showing the 10 hostages, sitting under the banner of the group. The group didn't say what were the nationalities of the hostages, or where they were captured.
The Kirkuk car bombing Saturday was the third this week targeting Iraq's beleaguered security forces, seen as collaborators with the United States and its allies.
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.
At least 19 people were killed and 67 wounded, the Health Ministry said. The street was strewn with bloodied bodies, twisted metal and shards of glass. Ambulances with sirens wailing rushed to the scene, where firefighters doused the flames.
The attack occurred as recruits were lining up to read the lists of those who had passed the physical fitness test, said Rustem Abdellah, one of the job-seekers who suffered burns to his face and chest.
"I am a graduate from the oil institute," Abdellah, 33, 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."
Earlier, a roadside bomb exploded in a small downtown side street, killing one man and seriously wounding two in a passing car, police and witnesses said.
Residents identified the three men as Iraqis who worked as security guards at the nearby al-Sadir Hotel, a heavily fortified complex where U.S. civilian contractors and other Westerners involved in Iraq's reconstruction effort live and work.
A mortar shell also 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.
The Americans insisted Saturday that 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.