Two Spaniards held in northern Mali by Al-Qaeda of the Islamic Maghreb (AQIM) for nearly eight months are "doing well", Deputy Prime Minister Maria Teresa Fernandez de la Vega said Friday.

"The two Spanish aid workers are doing well. The Spanish government continues to work daily to secure their release," she told a news conference.

She said the Spaniards were being held by a different group to one allegedly holding a 78-year-old French hostage that French-backed Mauritanian forces attacked in the North African desert Thursday.

She would however not comment further on the military assault, in which six members of the attacked Al-Qaeda-affiliated gang were killed.

"You will understand that I will not be more explicit," she said.

The French defence ministry said the group was refusing to negotiate the release of the French aid worker kidnapped four months ago, and had been responsible for the murder of a British hostage last year.

There was no word on the fate of the French captive, who does not appear to have been present when Thursday's pre-dawn assault was launched, and Mauritania said that the operation was not intended as a rescue.

Three Spanish aid workers, two men and a woman, were abducted in Mauritania on November 29 and subsequently taken to Mali.

The woman, Alicia Gamez, 39, was released in March after three months in captivity while the two men, Albert Vilalta, 35, and Roque Pascual, 50, are still in the hands of the Islamist group.

Al-Qaeda in the Islamic Maghreb (AQIM), the North African affiliate of Saudi-born militant Osama bin Laden's loose network of Islamist groups, claimed responsibility for the kidnapping in December.