"We confirm that Abdullah al-Senussi has been returned to Libya. A short time ago he was delivered to the office of the prosecutor general. He will undergo routine medical examination before questioning begins immediately afterwards," Taha Baara told AFP. "We will decide his fate afterwards."

Earlier, Mauritanian state television reported that the authorities there had handed Senussi over months after he was arrested for entering the country illegally.

"His extradition took place following the decision of the Mauritanian courts and its ratification by Mauritanian President Mohamed Ould Abdel Aziz," Baara said.

Senussi, a brother-in-law and feared former right-hand man of the slain Libyan dictator, was arrested in the Mauritanian capital Nouakchott in March and charged two months later for illegal entry and use of forged documents.

The ICC says Senussi, the former head of military intelligence in Libya, played a "crucial" role in attempting to crush the popular revolt that eventually ousted the Kadhafi regime late last year.

In the arrest warrant issued last June, the ICC said Senussi was an "indirect perpetrator of crimes against humanity, of murder and persecution based on political grounds" in the eastern Libyan city of Benghazi.