Moussa Ibrahim, the spokesman for late leader Muammar Gaddafi, has been captured, according to the office of Libya’s prime minister.
The office said he had been arrested by government forces in Tarhouna, 65 km (40 miles) south of Tripoli.
Other Libyan officials say they are skeptical, as such reports have proved false in the past.
The prime minister’s office did not provide any photographic or video evidence of the reported capture.
“Moussa Ibrahim has been arrested by forces belonging to the Libyan government in the town of Tarhouna and he is being transferred to Tripoli to begin interrogation,” a statement issued by the office of Prime Minister Ali Zidan said.
Tarhouna is located between Tripoli and Bani Walid – one of the last strongholds of pro-Gaddafi forces in the closing stages of last year’s conflicts.
During the war in Libya last year, Moussa Ibrahim held regular press conferences in Tripoli at the Rixos hotel, which was used by many international journalists.
He was last seen there shortly before the fall of Tripoli in August 2011.
The reported taking of Moussa Ibrahim comes on the first anniversary of Col. Gaddafi’s capture. The latter was seized and killed near his hometown of Sirte.
Interim leader Mohammed Magarief said that one year on, the country has not yet been fully liberated.
Militia groups which helped to defeat pro-Gaddafi forces remain powerful in many parts of the country. There have been clashes between militias in Bani Walid in recent days.