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. A video apparently showing hostage Bernard Planche held at gunpoint was broadcast by Arab channel Al-Arabiya. The channel said the previously unknown armed group had demanded the withdrawal of French troops from Iraq. France has not sent forces to the country. Mr Planche was abducted by gunmen from his home in Baghdad's Mansour district.