The release of Abdul Ghani Baradar -- the former right-hand man of Taliban founder Mullah Omar, who died in 2013 -- came less than two weeks after US envoy Zalmay Khalilzad met with the group's representatives in Qatar to discuss ending the Afghan conflict.

Baradar was among several senior Taliban leaders freed this week, after the Taliban demanded their release in direct talks with Khalilzad on October 12, a senior Taliban leader told AFP on the condition of anonymity.

"We believe that they were released at the US's request," the leader said.

He said Baradar would likely stay in Pakistan and shuttle between the Taliban's Doha office, Kabul and Islamabad.

"It was important for confidence building and all three will participate in the next round of talks with the US in Qatar," he added.

Baradar was the most high-profile Afghan Taliban leader detained by Pakistan since the 9/11 attacks in 2001.

He was arrested in the southern port city of Karachi in 2010, reportedly in an operation that was described as a huge blow to the militant group, which ruled Afghanistan from 1996-2001 when it was toppled by a US-led invasion.

It was not clear what role, if any, he would play in peace talks.

"Baradar was freed yesterday afternoon and he joined his family," Afghan Taliban spokesman Zabihullah Mujahid told AFP in a WhatsApp message.

A Pakistani intelligence official also said Baradar was "released a couple of days ago".

Baradar's release comes after the recent election of Pakistani Prime Minister Imran Khan, who has long advocated talks with the Taliban and other Islamist insurgents in the region to bring an end to years of fighting.

Pakistan's Foreign Minister Shah Mehmood Qureshi earlier this month also pledged to support negotiations with the Taliban as the country lobbies the United States to restore military aid.

The United States has long pressed Pakistan to crack down on the Taliban and other militant groups, which Washington says have safe havens in Pakistan's border areas and links to its shadowy military establishment -- charges Islamabad has repeatedly denied.

Khalilzad met with Taliban representatives in Doha as part of a regional trip designed to coordinate efforts to convince the group to negotiate an end to the war.