A video released by the North African arm of al-Qaeda apparently shows seven Western hostages are still alive.

According to BBC News, Mauritanian news agency ANI, which received the footage, said it shows four Frenchmen kidnapped from a uranium compound in Niger three years ago.

All the captives, including a Dutchman, a Swede and South African, who were kidnapped in northern Mali in November 2011, seemed in good health, ANI said.

The French foreign ministry said it believed the video was credible.

The video was apparently sent to ANI by the al-Qaeda in the Islamic Maghreb (AQIM).

"Based on an initial analysis, the video seems credible to us and provides new proof of life of the four French hostages kidnapped in Arlit (northern Niger) on 16 September 2010," French foreign ministry spokesman Philippe Lalliot said.

It was not clear when the video was made, but ANI said the messages recorded by the French hostages were made in June.

In the video, French national Daniel Larribe, 61, said: "I am in good health but threatened with death.''

He said that he held French authorities responsible for his fate, ANI reported. He gave no further details.

The three other French hostages were named as Pierre Legrand, Thierry Dol and Marc Feret.

Dutch hostage Sjaak Rijke, Swedish hostage Johan Gustafsson, and South African hostage Stephen Malcolm were kidnapped nearly two years ago from a hostel in Timbuktu in an attack that left a German man dead.

This is the first video said to show the men since France sent troops to Mali in January, after al-Qaeda-linked militants threatened to overrun the capital Bamako.

French President Francois Hollande said in July that France was "doing everything" to secure the hostages' release but would not comment further for fear of complicating "a situation which is bad enough".