The Philippines' top diplomat in Iraq has confirmed that a Filipino national has been taken hostage there.
Al-Jazeera said Iraqi gunmen had seized a Filipino
The man was shown surrounded by masked gunmen on a videotape broadcast by Arabic satellite channel al-Jazeera.
The video said he would be killed unless Manila withdrew its troops from Iraq within 72 hours.
Philippines President Gloria Arroyo has stopped any more Filipinos going to work in Iraq in response to the incident.
Ricardo Endaya, the Philippines charge d'affaires in Baghdad, did not give the hostage's identity.
But he said the Philippines authorities had been indirectly in touch with the kidnappers.
Filipino workers planning to travel to Iraq have been forced to turn round
"Technically, we are not yet negotiating with the hostage takers, but we have already established lines of communication with them through intermediaries," Mr Endaya said in a television interview.
President Arroyo earlier imposed a ban on all travel to Iraq after the news broke.
The Philippines has 51 soldiers and police in Iraq. Several thousand Filipino civilians work there.
Al-Jazeera showed a videotape of three gunmen and a man dressed in an orange jumpsuit kneeling in front of them.
Behind them was a banner that said the group's name was the Iraqi Islamic Army - the Khaled bin al-Waleed corps. It has not been heard of previously.
The channel reported that the group claimed it had already killed an Iraqi security guard accompanying the Filipino, who it said worked for a Saudi Arabian company linked to US forces.
The Associated Press news agency reports that the videotape displayed the hostage's Philippines identity card, which gave his name as Hafidh Amer, suggesting he may be a Muslim.
The seizure of the Philippines national is the latest in a spate of kidnappings of foreigners in Iraq.
On Tuesday, al-Jazeera apparently received a video of an Egyptian truck driver taken hostage in Iraq by a group calling itself the Iraqi Legitimate Resistance.
The Associated Press said it had seen the video, in which a man, who identifies himself as Alsayeid Mohammed Alsayeid Algarabawi, stands surrounded by armed, masked men.
Meanwhile, there is still no news of a Lebanese-born US marine reported killed at the weekend but who is, according to his family, alive and has been freed.