ISLAMABAD, Pakistan -- The Afghan Taliban claimed on Wednesday that Pakistan is keeping the group's former deputy leader under detention despite announcing his release last month, an allegation promptly denied by Pakistani officials.

Mullah Abdul Ghani Baradar's release after years in detention had stirred hope among many Afghan and Pakistani officials that this would help the struggling peace process in neighbouring Afghanistan.

But the current friction raises questions about whether that will happen.

Taliban spokesman Zabiullah Mujahid said in a statement on the group's website that Baradar "is still spending days and nights locked up behind bars in worrisome health conditions which are deteriorating by the day." He called for Baradar's immediate release.

Pakistani officials said Baradar is free but living under tight security for his own safety. The former Taliban commander was free to travel anywhere he chooses, but was always accompanied by Pakistani security officials, said a senior government official.

Pakistan has provided him a "secure place" to live that is not accessible to the general public, said a security official. The officials spoke on condition of anonymity because they were not authorized to talk to the media about the issue.

Afghan President Hamid Karzai said on Monday that Baradar has been released, "but he is still not completely free."

"We know that his family members have contact with him and we are trying to contact him, or find a telephone number, so we can use him for the peace process," Karzai said during a press conference in Kabul.

Kabul has demanded Islamabad free Baradar ever since he was arrested in a joint raid in the southern Pakistani city of Karachi in 2010 after holding secret peace talks with the Afghan government. Pakistan resisted for years, exacerbating already tense relations with neighbouring Afghanistan.

While some hope Baradar's release will help the peace process, others doubt it will do much good. The United States, which opposed his release, is worried he could return to the battlefield. That could give the Taliban in Afghanistan a boost at a time when the U.S. is drawing down its troops and increasingly relying on Afghan forces to fight insurgents.

The U.S. asked Pakistan to keep Baradar under house arrest rather than set him free, senior Pakistani and American officials have said, speaking on condition of anonymity because they were not authorized to talk to the media. It's unclear whether Baradar's tight security is related to that request.

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.

For Pakistan, the releases ended up causing friction with Kabul -- and Washington -- which were both frustrated that Pakistan was not monitoring the whereabouts and activities of the former inmates. Pakistani officials have said they felt slighted by the criticism because there was no request to keep tabs on the prisoners.