Tripoli - Niger on Friday handed over to Libya slain dictator Muammar Gaddafi's former chief of internal security Abdullah Mansur, the Libyan government announced.
A government statement said Tripoli had given the authorities in Niamey evidence implicating Mansur "in planning terrorist acts aimed at destabilising Libya".
It said Niamey decided that the former official "had violated commitments he had made" and had "not respected the conditions of his exile".
The government in Tripoli said it guaranteed Mansur "every right to a fair trial that conforms to international conventions".
It said he was now the responsibility of the prosecutor general and the justice system.
Mansur had been a secretary and adviser to Gaddafi, as well as a media official under the veteran strongman who was killed by rebels after being overthrown in 2011.
It was during the rebellion that he rose to become Gaddafi's head of internal security.
The government charges that Mansur is implicated in violence in southern Libya, where Gaddafi supporters briefly seized control of the region's main air base earlier this year.
On 5 February, Niger called for Western intervention to eradicate a growing threat from Islamist fighters who have established bases in southern Libya since Gaddafi's overthrow.
The impoverished but mineral-rich former French colony bordering southern Libya has had to contend with numerous Islamist attacks and kidnappings, some of which have threatened the security of its uranium production.
Other countries in addition to Niger have also handed over former Gaddafi-era officials.
Mauritania surrendered Abdullah al-Senussi, his ex-head of intelligence, and Tunisia handed over his former prime minister, Baghdadi al-Mahmudi.
Human rights groups have repeatedly criticised the conditions in which such former officials are held.
Human Rights Watch on Thursday urged Tripoli to allow Seif al-Islam, Gaddafi's son and one-time presumed heir, as well as others detained to have access to lawyers.