GAZA CITY, Gaza Strip - An unknown militant group demanded the release of Muslim prisoners in US jails within 72 hours in exchange for two kidnapped Fox News journalists, who were shown sitting cross-legged and barefoot on the floor in a video released Wednesday.

A video grab shows two Fox journalists, correspondent Steve Centanni (R) and New Zealand cameraman Olaf Wiig, speaking in an undisclosed location.[Reuters]

The video, which broke 10 days of silence from the kidnappers, marked the first time militants in Gaza have issued demands going beyond the conflict with Israel. The footage also had none of the trappings of locally produced videos, such as flags or masked gunmen, raising the possibility that foreign extremists may have taken root in Gaza.

Palestinian and Israeli officials say al-Qaida has been trying to infiltrate Gaza in the aftermath of Israel's withdrawal a year ago. The Egypt-Gaza border is now rife with smuggling tunnels, and Palestinian militant groups have blown up a border wall to allow people in and out of the area.

In the footage, American correspondent Steve Centanni, 60, of Washington, D.C., and cameraman Olaf Wiig, 36, of New Zealand appealed for help in getting released.

The images of the men sitting in a dark, drab room were the first sign of the journalists since they were abducted Aug. 14 from their TV van in Gaza City.

"Our captors are treating us well," Centanni said.

In a statement attached to the video, a group calling itself the Holy Jihad Brigades railed against the U.S. wars in Afghanistan and Iraq and characterized them as a war against Islam. It made no demands of Israel.

Local militant groups routinely try to limit the conflict to a fight between Palestinians and Israel, fearing they could otherwise cause a backlash against the Palestinian cause. Major militant groups, including the ruling Hamas movement, have all condemned the kidnapping and called for the journalists' release.

Militants with ties to Hamas have been involved in kidnappings in the past, including the June 25 abduction of an Israeli soldier, aimed at winning the release of Palestinians from Israeli jails.

However, Ghazi Hamad, a spokesman for the government, criticized the kidnapping of the Fox journalists. "Our battle is against the occupation inside the Palestinian territories, and we are not taking our battle outside the Palestinian land," he said.

Boaz Ganor, an Israeli counterterrorism expert, said the absence of Palestinian demands in the statement made it "much more likely that this is part of an outside group." Ganor said that since Israel's withdrawal from Gaza, Islamic militants with direct or indirect links to al-Qaida have sneaked into the territory. "They're now well-rooted in the Gaza Strip," he said.

Over the past two years, Palestinian militants have seized more than two dozen foreigners, usually to settle personal scores, but released them unharmed within hours. The holding of the Fox journalists is the longest so far.

A Palestinian security official close to the investigation said there were several signs that an outside group was behind the kidnapping. He noted the professional quality of the video and the absence of flags, masked gunmen or logos typically seen in videos made by local groups.

But the official said it was possible that local militants were trying to divert attention. He spoke on condition of anonymity because he was not authorized to discuss the matter with the press.

Palestinian security officials said they were analyzing the video and even turned to Islamic experts for help in deciphering the poetic verses from the Quran, the Muslim holy book, in the statement.

The kidnappers of Centanni and Wiig demanded that Muslim prisoners in U.S. jails be released within three days in exchange for the hostages. The group did not say what would happen if the deadline passes.

"You have angered us and we are not among those who wilt when angered, but the fountains of Islam erupt within us," the statement said.

"We are going to exchange the female and male Muslim prisoners in American jails for the prisoners that we have. We are going to give you 72 hours, beginning midnight tonight, to make your decision," it says. "If you implement and meet our condition, we will fulfill our promise."

It was not clear whether the group was referring to prisoners being held by the United States in Guantanamo Bay or Iraq, where the U.S. is holding large numbers of Muslim prisoners.

In Washington, the State Department said it would not accede to the demands.

"We don't make concessions to terrorists, and we continue to call for the release of these journalists without conditions," State Department press officer Gonzalo Gallegos said.

Fox News Senior Vice President John Moody said he was "encouraged that our colleagues appear to be alive and well."

"We trust that the abductors understand they are responsible for Steve and Olaf's welfare and safe return. We ask for their immediate release," he said.

In the video footage, the men, sitting on the floor in sweat suits, appear to be in good health. Centanni said the two men had access to clean water, showers, bathrooms, food and clothing.

"So, just want to let you know I am here and alive and give my love to my family and friends and ask to do anything you can to try to help us get out of here."

Wiig called for help to get them freed.

"If you could apply any pressure on the local government here in Gaza and the West Bank that would be much appreciated by Steve and myself," Wiig said.

Centanni's brother, Ken, said he was relieved to have received a sign of life. "We're very relieved that the kidnappers have contacted the world and we can see our brother and Olaf," Ken Centanni said from his San Jose, Calif., home.