Al-Jazeera TV aired a tape dated Jan. 21 showing the four workers--two Canadians, an American and a Briton--from the Chicago-based Christian Peacemaker Teams who disappeared Nov. 26. The previously unknown Swords of Righteous Bridges claimed responsibility for kidnapping them.
The news reader said the group issued a statement with the tape saying it was the "last chance" for U.S. and Iraqi authorities to "release all Iraqi prisoners in return of freeing the hostages, otherwise their fate will be death."
No deadline was set.
Canadian hostages James Loney, 41, and Harmeet Singh Sooden, 32; Tom Fox, 54, of Clear Brook, Va.; and Norman Kember, 74, of London, had been warned repeatedly by Iraqi and Western security officials before being abducted that they were taking a grave risk by moving around Baghdad without bodyguards.
The footage showing the men was gray and apparently shot using the camera's night-vision function. It showed each of the four men standing near a wall, before cutting away to another shot in which they were seated and talking but their voices were not heard.
Carol Rose, a U.S.-based coordinator for Christian Peacemaker, said she could not comment immediately as they were still waiting to see the tape.
Al-Jazeera editor Saad al-Dosari declined to say how the station obtained the tape, which was about 55 seconds long. He said the entire tape aired.
Christian Peacemaker Teams has been working in Iraq since October 2002, investigating allegations of abuse against Iraqi detainees by American and Iraqi forces. Its teams host human rights conferences in conflict zones, promoting peaceful solutions.
More than 250 foreigners have been taken hostage in Iraq since the 2003 U.S.-led invasion that toppled Saddam, and at least 39 have been killed.
Among the hostages still unaccounted for is American reporter Jill Carroll, 28, who was abducted Jan. 7 in Baghdad. Her kidnappers have demanded the release of all Iraqi women in custody.
The U.S. military said this week's release of five Iraqi women from military custody was coincidental and not in response to the ultimatum.
Family and friends of the hostages said they were encouraged that the videotape aired Saturday shows them alive, but they worried about the latest threat to kill them.
"We're still very concerned but at least we have proof that they are alive," Loney's brother, Matthew, said in a telephone interview from Vancouver, British Columbia.
"The four look to be OK, but it looks like they have lost weight," Matthew Loney said.
Rebecca Johnson, a Canadian-based coordinator for Christian Peacemakers, said the they were grateful to see the hostages alive.
"This news is an answer to our prayers. We continue to hope and pray for their release," she said.
Johnson blamed the U.S.-British-led occupation of Iraq for their abductions.