NOUAKCHOTT, April 15 (Reuters) - - Muammar Gaddafi's intelligence chief Abdullah al-Senussi, who was arrested in Mauritania last month and is sought by Libya, France and the International Criminal Court (ICC), is ill, Mauritanian President Mohamed Ould Abdel Aziz said on Sunday.

Libyan authorities are seeking the extradition of Gaddafi's former right-hand man, vying with Paris and the Hague-based ICC which also have legal cases against him.

Abdel Aziz said in an interview with the French TV5 station that Senussi, 62, already had health problems when he flew into Mauritania's capital Nouakchott in March using a false passport.

"His situation is stationary, it's not worrying," the Mauritanian president said. "We've had him examined by doctors, as soon as the justice system has finished with him, we'll take a decision," he added.

He did not say what ailment Senussi was suffering from, but sources familiar with Senussi's case told Reuters in Nouakchott he was believed to have cancer.

In March, a senior Libyan government official said after talks with Mauritania's Abdel Aziz that the latter had given his consent for Senussi's extradition to Libya. But Mauritanian officials have denied any such commitment was given.

"His case is being studied. We have a number of questions to put to him and we haven't finished with him yet. We haven't taken our decision yet," Abdel Aziz told TV5.

Senussi is suspected of playing a central role in the killing of more than 1,200 inmates at Tripoli's Abu Salim prison in 1996. It was the arrest of a lawyer acting for relatives of the victims that sparked Libya's revolt in February last year.

France wants Senussi in connection with a 1989 airliner bombing over Niger in which 54 of its nationals died.

Senussi has also been linked to the 1988 bombing over Lockerbie, Scotland of a Pan Am jet that killed 270 people. Diplomatic sources have said the United States was keen to question him about that attack.