Al-Jazeera television aired a new videotape Friday in which kidnappers of four Christian peace activists threatened to kill their hostages unless all prisoners in US and Iraqi detention centers are released. The kidnappers gave the two governments until Thursday Dec. 8 to meet their demands, according to Al-Jazeera quoting a statement delivered with the tape. "It gave a deadline for those concerned until 8 Dec. to meet the demands," an Al-Jazeera correspondent said. The tape showed what the television station said were two Canadian hostages. An American and a Briton are also being held.