A previously unknown Palestinian militant group, the Holy Jihad Brigades, says it is behind the kidnapping of New Zealand cameraman Olaf Wiig and his Fox News colleague.
Wiig, 36, and American correspondent Steve Centanni, 60, were abducted in the Gaza Strip nine days ago.
In a video sent to Arabic television stations, the captured men say they are in "fairly good health, and appealed for help to secure their freedom. In a fax to news agencies, the Holy Jihad Brigades has demanded the United States release Muslim prisoners in US prisons within 72 hours, in return for the men.
The pair are shown sitting on a mat on a floor, against a black
backdrop with no markings. No militants could be seen.
"We're alive and well, in fairly good health," Centanni said, speaking in a clear and calm voice.
Centanni said they had been treated well.
Wigg sends his love to family and friends and asks them to do anything they can to get them released.
Wiig added: "I know my family will already be doing this, but if you could apply any political pressure ... both here in Gaza and the West Bank that would be much appreciated by both Steve and myself."
The United States said it would not make "concessions to
terrorists". The militant group did not say what would happen if
the demand was ignored.
The video bore many hallmarks of tapes of captives issued by militants in Iraq, and the rhetoric of the group also mirrored the heavily religious language used by Iraqi insurgents.
Centanni and Wiig were abducted by masked gunmen in Gaza City on
August 14 as they were working on a story.
"Release what you have, and we will release what we have," the Holy Jihad Brigades said in a statement obtained by Reuters.
"If you implement our conditions we will implement our promise, otherwise you will have to wait."
The United States called for the quick release of the two men and vowed not to bow to the demands.
"It is the position of the US government that we do not make concessions to terrorists," said Micaela Schweitzer-Bluhm, spokeswoman for the US consulate in Jerusalem.
Until Thursday's statement from the militant group, which contained verses from the Koran, no one had claimed responsibility for the abduction, which is now the longest-lasting in Gaza for more than a year.
Previous kidnappings have usually ended after a few hours, or at most a few days of captivity. There have been at least seven involving foreigners since August 2005, when Israeli troops withdrew from Gaza after 38 years of occupation.
Palestinian leaders including Prime Minister Ismail Haniyeh of the militant Islamist group Hamas have called for the release of the two captives. Palestinian security forces have been scouring Gaza for them.
Hamas said it was unaware of the Holy Jihad Brigades.
"We reject and condemn the kidnapping of foreigners and journalists and we urge the kidnappers to immediately free them," Hamas spokesman Sami Abu Zuhri said.
British and American reporters have been warned not to go to Gaza or to take extra precautions because of credible threats of additional kidnappings, Western diplomats said this week.
Palestinian militant groups that have briefly kidnapped foreigners in the past have usually done so over local grievances such as demands for jobs or the release of family members from Palestinian jails.