Updated

Pakistan released its highest-ranking Afghan Taliban prisoner on Saturday in an effort to jump-start Afghanistan's struggling peace process, Pakistani officials said.

The Afghan government has long demanded that Pakistan free Mullah Abdul Ghani Baradar, the Taliban's former deputy leader who was arrested in a joint raid with the CIA in the southern Pakistani city of Karachi in 2010.

Pakistani intelligence and security officials confirmed that he left detention Saturday but did not provide any details, including where he was held. They spoke on condition of anonymity because they were not authorized to talk to the media.

Pakistan's Foreign Ministry announced earlier that Baradar would be released Saturday "to further facilitate the Afghan reconciliation process," but also didn't provide any details.

Mohammad Ismail Qasimyar, a member of the council tasked by the Afghan government to negotiate with the Taliban, praised Baradar's release, saying "we are very much hopeful that Mullah Baradar can play an important role in the peace process."

Wakil Ahmad Muttawakil, who served as foreign minister for the Taliban when the group ruled Afghanistan, also hailed Bardar's release and cautioned Pakistan not to try to control his movements now that he is free.

"They also have to allow him contact with Taliban leaders and for him to be useful for peace in Afghanistan," Muttawakil told The Associated Press.

Pakistan has released at least 33 Taliban prisoners over the last year at the Afghan government's request in an attempt to boost peace negotiations between the insurgents and Kabul.

But there is no sign that the previous releases have helped peace talks, and some of the prisoners are believed to have returned to the fight against the Afghan government. The U.S. was reluctant to see Baradar released, believing he would also return to the battlefield.

Afghanistan has in the past called on Pakistan to release Taliban prisoners into its custody. But they have instead been set free in Pakistan, and it was likely the same would happen with Baradar.

Afghanistan's Foreign Ministry spokesman Janan Mosazai has said Baradar must be "accessible, secure and with a known address" if he remains in Pakistan.

The circumstances surrounding Baradar's arrest in Karachi were murky. Afghan officials said at the time that he was holding secret peace talks with the Afghan government and accused Pakistan of arresting him to sabotage or gain control of the process. Others said the U.S. was the driving force behind his arrest.

Pakistan is a key player in Afghan peace talks because of its historical ties to the Taliban. Islamabad helped the Taliban seize control of Afghanistan in 1996 and is widely believed to have maintained ties with the group, despite official denials.

But there is also significant distrust between the two, and Pakistan has arrested dozens of Taliban militants in the years following the U.S.-led invasion of Afghanistan in 2001 -- possibly to hold as bargaining chips.

Pakistan has increasingly pushed for a peace settlement because it is worried that chaos in Afghanistan following the withdrawal of most U.S. combat troops by the end of 2014 could make it more difficult to fight its own domestic Taliban militants. It could also send a flood of new refugees into Pakistan.

The most recent attempt to push forward peace negotiations foundered in June in the Qatari capital of Doha. The Afghan president pulled the plug on the talks even before they began because he was angered that the group marked the opening of its Doha political office with the flag, anthem and symbols of the Islamic Emirate of Afghanistan -- the group's name when they ruled the country.