DAKAR (Reuters) - A video appearing to show seven French citizens, including four children, kidnapped in Cameroon last week was posted on the YouTube website on Monday.

In the video, a male hostage says the group was taken by Nigeria's Boko Haram militants who were demanding the release of Islamist militants jailed in Nigeria and Cameroon. One of the apparent kidnappers warned the hostages would be killed if their demands are not met.

(Reporting by Bate Felix and John Irish in Dakar, Asma Alsharif in Cairo; Writing by David Lewis; Editing by Jon Hemming)