(CNN) -- Niger has extradited Moammar Gadhafi's son Saadi, who has been transferred to a jail in Tripoli, Libya, the Libyan government said Thursday.
The North African country had been seeking the handover of Saadi Gadhafi, who fled across the border to Niger when rebel forces toppled his father in a NATO-backed uprising in 2011.
"He was handed to Libya and is now in the custody of the Libyan judicial police," the Libyan government said on its Facebook page.
It thanked the leader of its southern neighbor for his cooperation.
Saadi, one of Gadhafi's seven sons, was a professional soccer player and businessman before his father's downfall. Unlike his brother, Saif al-Islam, Gadhafi's heir apparent, he is not wanted by the International Criminal Court in The Hague, Netherlands, on charges of war crimes.
In late 2011, rebel forces captured Saif al-Islam, who remains in a militia hands in the small western mountain town of Zintan, Libya.
Niger handed over Saadi Gadhafi after Libyan authorities provided evidence of "communications and practices targeting Libya's security and aimed at destabilizing Libya," Libyan Prime Minister Ali Zeidan told Libyan television.
In February 2012, the younger Gadhafi made a televised phone call warning of an imminent uprising in Libya, saying he was in regular contact with people in the country who were unhappy with the new authorities.
Authorities in Niger had warned him after that incident. He had been staying under tight regulation, including house arrest.
Pictures of Saadi Gadhafi, 40, wearing a blue uniform as his head was shaved circulated widely on social media.
Niger had previously refused to hand him over, with some officials saying he could face the death penalty in Libya.
He reportedly resided in a secured guesthouse in Niger's capital, Niamey, after fleeing across the Sahara desert.
A leading human rights group questioned why he had been handed over.
"The authorities in Niger should explain why they were convinced that Saadi Gaddafi would not be mistreated and would get a fair trial," said Sarah Leah Whitson, Middle East and North Africa director at Human Rights Watch.
She called for Libyan officials to bring him quickly to trial and protect him from inhumane treatment.
Seeking Gadhafi supporters
Since the end of the conflict that came with Moammar Gadhafi's capture and killing in October 2011, Libya's government has sought the extradition of family members and ex-officials.
Several of Gadhafi's other sons were killed during the rebellion.
Saif al-Arab died in a NATO airstrike in spring 2011, and Khamis, who led the elite and widely feared Khamis brigade, was reported killed during the fighting. He died in a battle in northwestern Libya that August.
Around the time of his death, troops commanded by Khamis Gadhafi killed an estimated 150 captive civilians during a retreat, hurling grenades and spraying bullets into a building full of men they had promised to release, a survivor said.
Another son, once national security adviser, Mutassim, was killed near the Libyan leader's last stronghold of Sirte in October 2011.
The former dictator's wife, Safia, fled with sons Mohammed, Hannibal and daughter Aisha to neighboring Algeria in late August 2011, along with extended family members.
They reportedly left there for Oman, where they were granted asylum.
CNN's Jomana Karadsheh contributed to this report.