Abdul Wakil Omari, a spokesman for the Afghan Supreme Court, said the men would be formally handed over during a ceremony at the court later Tuesday. He did not say how many prisoners had been released, but other officials put the number at 17.
"There are 17 of them and they are being handed over to the Afghan National Security Council (search)," a senior Afghan official told The Associated Press on condition of anonymity. The security council oversees the country's various intelligence agencies.
It was not clear if the men will face charges in their home country. The U.S. military had no immediate comment, referring all questions to Afghan authorities.
In late March, the Pentagon declared that 38 Guantanamo Bay prisoners were no longer considered "enemy combatants" — the bulk of them from Afghanistan and Pakistan. Five of those men had already been sent home, but the other 33 remained at the U.S. Navy base awaiting transportation.
It was not immediately clear if the 17 Afghans being turned over Tuesday were from that group.
The U.S. military has released more than 200 detainees from Guantanamo, but many — including dozens of prisoners sent to the United Kingdom, Russia, France, Morocco, Saudi Arabia and Pakistan — are freed on the condition they will be held by their home countries.
Some 38 Pakistanis — including at least 29 released from Guantanamo Bay in September — are still being held in their home country, most without charge. The government has said it is "debriefing" the men.