Al Jazeera television has broadcast an interview with a man claiming to have visited leaders of guerrillas holding three Japanese prisoners today, who said they told him they would kill the hostages within 24 hours.
A man described as Muzhir al-Duleimi, head of the League for the Defence of the Rights of the Iraqi People, told a correspondent for Al Jazeera in Baghdad that previous reports that the hostage-takers were about to free the Japanese had been untrue.
"This morning we visited the fighters and we discovered that everything reported yesterday is absolutely not true and the resistance leadership said it would not release the hostages," said Duleimi, whose group is previously unknown.
It was not clear when the 24-hour deadline would expire.
On Thursday, the militants issued a videotape showing them holding knives to the throats of the blindfolded prisoners and threatened to burn them alive unless Japanese troops were pulled out of Iraq in three days.
Duleimi said he had not personally seen the hostages on Sunday.
"I made an effort to save them today but the resistance said I had only 24 hours and gave me this statement... which says the (Japanese) vice foreign minister should visit Falluja to see the mass graves and massacres committed by American forces," he said.
"The Japanese government should apologize to the Iraqi people and withdraw forces from Iraq and they have 24 hours after which the first hostage will be killed and 12 hours later the rest of them will be killed."
Japan's Senior Vice Foreign Minister Ichiro Aisawa is in Amman, Jordan to deal with the hostage crisis. A Japanese government official said officials were checking the Al Jazeera report.