Paris — Islamist rebels in Nigeria released video of a French family kidnapped in Cameroon last week, leading France to blast the scene as one of "cruelty without limits."

The family members, three adults and four children-boys aged 5 to 12, are shown sitting on the ground inside a sort of tent.

The family is flanked by two masked men holding rifles, in front of them another masked hostage taker who reads out a statement in Arabic demanding the release of "brothers" and "sisters" and threatening twice to "slaughter those we took" unless the group's demands are met.

France's Prime Minister, Jean-Marc Ayrault, said experts were examining the video to determine whether it was authentic. "[We] have received information that the group Boko Haram is claiming to be holding the French family," Ayrault told reporters.