An Arabic satellite TV station, Al Jazeera, says the Iraqi militants holding three Japanese hostages have threatened to begin killing them unless their demands were met within 24 hours.

The Qatar-based TV, quoting a Japanese human rights activist, said the Iraqi resistance group has postponed its earlier deadline for killing the hostage for 24 hours, and that if the deadline passes unheeded within the next 24 hours, they would kill one hostage, and then kill another every 12 hours until their demands are met.

Hopes had been raised in Japan over the weekend following reports that the militants would soon free their captives due to appeals from Sunni clerics. But those hopes evaporated after the kidnappers issued a later statement threatening the impending killing of the hostages.

Quoting an unnamed Japanese government official, Japan's Kyodo news agency said a negotiator whose identity was not disclosed told the government that the three captives were safe for the time being.

Kyodo later quoted another unspecified government source as saying the three were being held near Fallujah, west of Baghdad, a city that has been the scene of fierce fighting in recent days between guerrilla fighters and U.S. forces.

The agency gave no more details and Japanese government officials were not immediately available for comment.