Iraqi militants are threatening to kill three Japanese hostages unless Tokyo withdraws its troops within three days.
The pictures were designed to shock
The three civilians were snatched by a group called the Mujahideen Brigades and Arab al-Jazeera TV showed them being held at knife-point.
Elsewhere, one Canadian and two Arabs were also kidnapped, but seven abducted South Koreans were released.
Our Baghdad correspondent says this is the first use of kidnappings for political ends in the conflict.
The gunmen holding the Japanese say they will burn their captives alive unless Japanese troops are withdrawn from Iraq.
The three are believed to be Noriaki Imai, an 18-year-old male volunteer worker, Nahoko Takato, 34, a female volunteer worker, and Soichiro Koriyama, a 32-year-old male freelance photojournalist.
Tokyo has said it is firm in its resolve to keep troops in Iraq despite the threat.
It is not clear whether any of the kidnap incidents are connected. Concern is also growing about the whereabouts of a British civilian who disappeared in the southern town of Nasiriya on Tuesday.
The BBC's Barbara Plett in Baghdad said the abductions were an alarming development for America's coalition partners, already worried by the unprecedented violence that hit Iraq this week.
They came as US-led coalition soldiers across Iraq were engaged in fresh clashes with Sunni and Shia militants.
The violence has left up to 300 Iraqis and at least 30 coalition troops dead. The US military said on Thursday it had suffered six more combat deaths, bringing the number of US soldiers killed in action since the start of the war to 449.
The senior American military officer in Iraq, Lt Gen Ricardo Sanchez, has acknowledged that the US-led forces no longer have full control over two southern towns after nearly a week of fighting Shia militia who support the cleric Moqtada Sadr.
Gen Sanchez said that the rebels were in partial control of the town of Najaf, and fully controlled the town of Kut after pushing out Ukrainian troops.
Coalition troops are engaged in clashes with insurgents across Iraq
Militiamen also control the town of Kufa, holding police stations and government buildings in the town, according to residents.
Gen Sanchez said his forces were pressing the militiamen in Najaf and would soon attack and retake control of Kut.
However, confidence is not running so high in Falluja, where Marine Lt Luke Pernotto told the BBC's Richard Lister that there were not enough US troops to keep pushing the insurgents back and they had summoned reinforcements.
The US has also rushed troops to the holy city of Karbala, to reinforce the hard-pressed Bulgarian and Polish troops based there.
Bulgarian Foreign Minister Solomon Passi said 120 US soldiers had been deployed to support his country's 480-strong contingent in the city, which has faced persistent attacks by Shia militia.
The violence comes as thousands of pilgrims are expected to flood the city over the weekend for religious ceremonies marking al-Arbaeen. It ends the mourning period for the Shia's most beloved saint, Imam Hussein, who was martyred in the 7th century.
In other developments:
- Iraqi Interior Minister Nuri Badran announces his resignation. Mr Badran, a Shia, said top Iraq administrator Paul Bremer wanted to redress an imbalance between Shias and Sunnis within the Iraqi Governing Council - but he was also "not satisfied with the performance of the interior ministry".
- Street fighting continues in the besieged Sunni town of Falluja where US troops launched a big operation on Monday.
- Arrangements are made to send relief supplies into Falluja.
- US helicopters destroy the Baghdad offices of radical Shia cleric Moqtada Sadr.
The BBC's Jonathan Head in Tokyo says the hostage-taking will be a "wrenching experience" for Japan.
It will put extreme pressure on Prime Minister Junichiro Koizumi, who took the decision to send the troops, despite the extreme misgivings of many Japanese citizens, our correspondent says.
Japan has about 550 troops on "non-combat" mission in Iraq. Their base in the southern town of Sumawa was attacked on Wednesday evening.
Falluja has been sealed off by US troops
About 500 South Korean army medics and engineers are currently deployed in Nasiriya.
South Korea is also preparing to send a combat-ready force of 3,000, but its deployment was delayed last month because of the deteriorating situation.
Sending troops to Iraq has been controversial amid signs of strain in the long military alliance between South Korea and the US.
The video showed the two Japanese men and a woman - sometimes blindfolded - in a room surrounded by gunmen. It is not known where they were picked up.
A statement by the Mujahideen Brigades said Japan had betrayed Iraqis by backing the US occupation of Iraq.
"We tell you that three of your children have fallen prisoner in our hands and we give you two options - withdraw your forces from our country and go home or we will burn them alive and feed them to the fighters," it said.
"You have three days from the date of this tape's airing."