France is "certain" that five French hostages seized in Niger by an al-Qaeda regional offshoot are still alive, President Nicolas Sarkozy told reporters on Monday.

"We believe that they are still alive. We are certain of it," he told reporters, adding that two French journalists held in Afghanistan for more than a year were also still alive.

The Niger hostages were seized in September along with a Togolese and a Madagascan colleague from the West African country's uranium mining town of Arlit and later taken across the border into Mali.

Their abduction was claimed by Al-Qaeda in the Islamic Maghreb (AQIM).

Al-Qaeda leader Osama bin Laden said in a tape broadcast on Al-Jazeera on Friday that the release of French hostages depended on a pullout of France's soldiers in Afghanistan.

The satellite channel said the Al-Qaeda chief was referring to the French journalists held in Afghanistan, although his message did not specify whether it also covered France's hostages seized in Africa.

Earlier this month, two 25-year-old Frenchmen kidnapped from a restaurant in the Niger capital Niamey were found dead in Mali after a failed attempt by French special forces to rescue them from an Al-Qaeda convoy.

At his first news conference since the deaths, Sarkozy said it had been one of the most emotionally difficult episodes of his presidency, but insisted he had had no choice but to order the assault as the gang would not negotiate.