A militant group in Iraq has threatened to kill a French water engineer seized three weeks ago, unless France ends its "illegitimate presence" in the country.
The hostage takers reportedly demanded French troops withdraw
A video apparently showing hostage Bernard Planche held at gunpoint was broadcast by Arab channel Al-Arabiya.
The channel said the previously unknown group had demanded French troops leave Iraq. France has no forces in the country and opposed the US-led war.
Mr Planche was abducted by gunmen from his home in Baghdad's Mansour district.
The video, an excerpt of which was aired on Al-Arabiya, showed a man with a moustache seated on a chair with gunmen to either side.
He spoke in English, saying: "My name is Bernard. I'm 52 years old. I'm French, from Lyons."
The man said he worked on water treatment projects in Baghdad and apologised for "problems" he had caused.
The name of a previously unknown militant group, Brigade of Monitoring for Iraq, was shown in one corner of the footage.
Mr Planche was working for a small non-governmental organisation called AACCESS when he was kidnapped on 5 December in Baghdad.
The French government has said it is working for his release.
"We demand the immediate release of Mr Planche as nothing can justify his being taken hostage in Iraq," said a foreign ministry spokeswoman.
"We are obviously going to examine the images broadcast by Al-Arabiya and we are going to do it very carefully."
France has tried to deter its citizens going to Baghdad since the kidnapping in 2004 of two French journalists, who were eventually freed after weeks in captivity.
Mr Planche's abduction came 10 days after that of a German archaeologist, Susanne Osthoff, who has since been released.
The fate of a group of four Christian peace activists seized a day after her remains unknown.
An armed group has also captured a Jordanian working as a driver for his country's embassy in Baghdad.