Images of four peace activists taken hostage in Iraq — one of which is an American — was shown on the Arab satellite station Al-Jazeera Tuesday.

A previously unknown group, the Swords of Righteousness Brigade, claimed responsibility for the kidnappings. The group said the four victims were spies working undercover as Christian peace activists, Al-Jazeera said. Station officials said they could not verify any of the information on the tape.

The aid group, Christian Peacemaker Teams, has confirmed that four of its members were taken hostage Saturday. Reports said one was an American, two were Canadian, and one was a Briton. The U.S. embassy in Baghdad had confirmed that an American was missing in Iraq.

The tape showed four men and a British passport belonging to someone named Norman Kember. The British government and the Christian Peacemaker Teams both said Kember was among the four activists taken hostage.

Christian Peacemaker Teams said it would not identify the other three for their protection.

"In the interests of their safety our Iraq team needs that space to locate them," group spokesman Rebecca Johnson said. "The communication that may be coming from us does not help them to locate them."

State Department spokesman Sean McCormack said Tuesday that he has seen the reports regarding the hostages but "our people have not had an opportunity to review the videotape to either confirm or deny its validity, whether or not the people who appeared in that videotape are the ones that the captors purport to say who they are."

Regarding the missing American, McCormack added: "Safe to say, we are in close contact with the American citizen's family and that we want to do everything that we can to see that this individual is returned to their family safe and sound."

A white-haired man shown in the passport photograph also was seen sitting on the floor next to three other men in the video, which had a date stamp indicating it was recorded Sunday.

In the corner of the video were two crossed black swords and the name of the group, Swords of Righteousness Brigade, written in red Arabic script.

Separately, photos were released Tuesday of Susanne Osthoff, a German woman, being led away blindfolded by armed captors. The photos were taken from a video in which her captors demanded that Germany stop any dealings with Iraq's government, according to Germany's ARD television. Germany has ruled out sending troops to Iraq and opposed the U.S.-led war.

Osthoff and her driver have been missing since Friday and "according to current information, we have to assume it is a kidnapping," German Chancellor Angela Merkel said in Berlin.

"One can only hope and keep their fingers crossed and remain optimistic," her mother, Ingrid Hala, told Germany N24 news station.

Germany's Central Council of Muslims called for Osthoff's immediate release.

On Monday, Iraqi Deputy Interior Minister Hussein Kamal said authorities had no leads. No group has claimed responsibility and details of the apparent kidnapping were unclear.

In other violence, six Iranian pilgrims were abducted by gunmen north of Baghdad.

Two U.S. soldiers were also killed in Iraq when their patrol was struck by a roadside bomb, according to U.S. military officials. The soldiers were members of Task Force Baghdad, and the attack took place north of Baghdad.

In Tarmiyah, 30 miles north of Baghdad, a homicide car bomber killed eight Iraqi soldiers and wounding five more when he drove into an army patrol, police Lt. Ali Hussein said. A U.S. Army medical helicopter helped evacuate the wounded, he added.

Christian Peacemaker Teams issued a statement Tuesday saying the four male peace activists captured were working on behalf of Iraqi civilians. The group said it has had a team in Iraq since October 2002, working with U.S. and Iraqi detainees and training others in nonviolent intervention and human rights documentation.

The statement said those taken hostage knew the risks when they went to Iraq.

"The team's work has focused on documenting and focusing public attention on detainee abuses, connecting citizens of Iraq to local and international human rights organizations, and accompanying Iraqi civilians as they interact with multinational military personnel and Iraq's government officials," the group said.

On Sunday, a Canadian official said two Canadians were in the group. U.S. Embassy spokeswoman Elizabeth Colton said only that an American had been reported missing, and the person's name and organization were being withheld.

Britain has said Kember, a retired professor, vanished in Iraq.

Kember is a longtime peace activist who once fretted publicly that he was taking the easy way out by protesting in safety at home while British soldiers risked their lives in Iraq.

In Barcelona, Spain, British Foreign Secretary Jack Straw said he had contacted Iraqi Foreign Minister Hohshyar Zebari about Kember's abduction, and that Zebari "pledged every assistance from the Iraqi government."

The Iranian pilgrims were abducted Tuesday morning near Balad, 50 miles north of Baghdad, police Maj. Falah Mohammedawi said, but it was not clear if the six were going to or coming from Samarra, a central city that houses a shrine to two Shiite saints.

Iraq and Iran, predominantly Shiite countries, reached an agreement earlier this year on pilgrim visits, which excludes trips to Shiite shrines in Baghdad and Samarra because of the dangerous security situation. The pilgrims appear to have been violating that agreement.

Iraq was rocked by a wave of foreigner kidnappings and beheadings in 2004 and early 2005, but they have dropped off in recent months as many Western groups have left and security precautions for those who remain have tightened. Insurgents, including Al Qaeda in Iraq, seized more than 225 people, killing at least 38 — including three Americans.

Insurgents have kidnapped aid workers, journalists and contractors in an attempt to drive foreigners out of the country or to win large ransoms.

Since May, abductions have fallen off considerably, mainly because many Western groups left Iraq and security precautions for those remaining have been tightened, with foreigners staying in barricaded compounds and moving only in heavily guarded convoys.

The last American to be kidnapped was Jeffrey Ake, a contract worker from LaPorte, Ind., who was abducted April 11. He was seen in a video aired days afterward, held with a gun to his head, but there has been no word on his fate.

FOX News' Teri Schultz and The Associated Press contributed to this report.