* Afghanistan believes Baradar key to peace process
* Pakistan announced his release late on Friday
* Baradar was one of the founders of Taliban insurgency (Adds Afghan comments, background)
ISLAMABAD, Sept 21 (Reuters) - Pakistan on Saturday released former Taliban second-in-command Mullah Abdul Ghani Baradar, a man Afghanistan believes could help tempt moderate Taliban leaders to the negotiating table and bring peace after more than a decade of war.
Pakistan's foreign ministry announced late on Friday Baradar - one of the founders of the Taliban insurgency - would be released a day later, and on Saturday, Pakistani television reported Baradar had been set free.
There was no official confirmation of his whereabouts.
"The Afghan government welcomes Pakistan's decision to release Mullah Baradar," said Aimal Faizi, a spokesman for Afghan President Hamid Karzai.
"This release has occurred because of the Afghan government's consistent pressure requesting that Mullah Baradar be set free," he said.
Baradar is at the heart of Afghan efforts to kick-start a stalled peace process as U.S.- led troops prepare to pull out at the end of next year and anxiety grows over the country's security.
Baradar was once a close friend of the reclusive Taliban leader, Mullah Mohammad Omar, who gave him his nom de guerre, "Baradar" or "brother".
Known as a pragmatic operator, he is believed to be willing to play the role of a peace ambassador, having once reached out to Kabul to seek a peace settlement. He was arrested in Pakistan in a joint U.S.-Pakistani security operation.
But critics say his years in detention may have eroded his sway over the fast evolving insurgency and there are doubts whether Mullah Omar would agree to talk to his former protégé.
He is still hugely respected by field commanders in Afghanistan, however, and a call from Baradar to lay down arms is likely to be treated seriously.
It is also not clear where Baradar would travel following his release. Sources in Pakistan have said he could be sent to Turkey or Saudi Arabia to help kick start peace talks with the Taliban after the breakdown of the Doha round of talks.
Afghanistan wants Baradar to be handed to authorities there, but Pakistan has refused to do so. "We hope that Mullah Baradar decides to come to Afghanistan," Faizi said. (Additional reporting by Dylan Welch in Kabul; Writing by Maria Golovnina; Editing by Clarence Fernandez)