The Libyan government says former leader Col Muammar Gaddafi's son, Saadi, has been extradited from Niger and is now in custody in Tripoli.
Pictures posted on the internet showed him having his head and beard shaved.
Saadi Gaddafi, the former head of Libya's football federation, fled after his father was killed in the 2011 revolution.
The 40-year-old is best known for a brief career in Italian football as well as his playboy lifestyle.
Saadi, one of Col Gaddafi's seven sons, is accused of shooting protesters and other crimes committed during his father's rule.
"The Libyan government received today Saadi Gaddafi and he arrived in Tripoli," the Libyan government said in a statement early on Thursday.
Two security sources later confirmed to the BBC's Rana Jawad that Saadi Gaddafi had been returned and was now in the hands of the Libyan judicial authorities.
Lawyer Nick Kaufman, who has previously represented Saadi and other Gaddafi family members, criticised the move, calling it a "rendition".
"I don't think that Saadi Gaddafi was afforded any form of legal process in Niger before his rendering to Libya," Kaufman said.
Niger had previously refused Libyan requests to extradite him, with the justice minister saying he was "certain to face the death penalty".
In 2012, Interpol issued a "red notice", obliging member countries to arrest him.
Saadi Gaddafi had reportedly resided in a state guesthouse in Niger's capital, Niamey, after fleeing across the Sahara desert.
Since the 2011 uprising, Libya's new government has sought the extradition of several Gaddafi family members and ex-officials, with mixed success.
Niger extradited Abdallah Mansur, a former top intelligence official, to Libya on 14 February.
He was one of 15 other officials sent back to Libya after Niger accused them of plotting against the new Libya govt
Mauritania also extradited Gaddafi's former intelligence chief, Abdullah al-Senussi, in January 2013.
Libya's deputy prime minister at the time was forced to deny that Mauritania had been paid to extradite Mr Senussi.
He said a 250m dinar (£120m; $200m) donation to Mauritania made several months after the extradition was to "help the Mauritanian economy".
Similarly, Libyan officials denied last year that a $2bn loan to Egypt had anything to do with the extradition of former Gaddafi officials days earlier.
Libya's highest-profile prisoner, Gaddafi's son Saif al-Islam Gaddafi, has been held in the mountain town of Zintan since his capture in November 2011.
While court proceedings against the prisoners have been initiated, trials have been set back by security concerns and procedural delays.
Meanwhile, Gaddafi's cousin and ex-envoy to Egypt, Ahmad Gaddaf-el-Dam, remains in Egypt despite Tripoli's attempts to secure his extradition.