Pakistan has detained a senior Afghan Taliban member in an attempt to put pressure on the militants amid talks with the US, sources in the group say.
Hafez Mohibullah, religious affairs minister when the Taliban ran Afghanistan before 2001, was held in Peshawar, the sources told the BBC.
The US has repeatedly called on Pakistan to end "safe havens" for the Taliban on its soil.
Pakistan denies backing the group to retain influence in Afghanistan.
The reported detention of Hafez Mohibullah comes ahead of a visit to Pakistan by US special representative for Afghanistan Reconciliation, Zalmay Khalilzad, who has held a series of meetings with the Taliban's political office in Qatar and the United Arab Emirates.
The US wants Pakistan to encourage the militants to reach a settlement in Afghanistan and bring the 17-year conflict to a close.
There was no immediate response from authorities in Pakistan.
Image captionThe US now relies heavily on air power in Afghanistan
Taliban sources say Hafez Mohibullah had been living in the city for a number of years.
Two high-ranking Taliban figures, talking on condition of anonymity, suggested the former minister had been detained to put pressure on the group into meeting Mr Khalilzad in Pakistan this week, and crucially to agree to meet representatives of Afghan President Ashraf Ghani.
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So far the Taliban have refused to hold direct talks with Afghan officials, whom they dismiss as "puppets" and have only met US officials. Sources within the group say both Pakistan and Saudi Arabia have been trying to convince the Taliban to change their stance.
One senior Taliban figure told the BBC: "They arrested him [Mohibullah] to send a message."
Another from the group's Quetta Shura, or leadership council, added: "There was a meeting with Pakistani officials on the upcoming peace talks which ended in arguments. Right afterwards, the authorities raided a number of houses and arrested Mohibullah. After that [Taliban leader] Sheikh Hibatullah sent a message warning everyone to be alert."
Previously Taliban officials have said they will only begin talks with the Afghan government once a firm date for the withdrawal of American troops from the country has been agreed.
Media captionTaliban "threaten 70% of Afghanistan", BBC investigation finds
The last set of negotiations between Mr Khalilzad and Taliban representatives took place in Abu Dhabi in December, with Pakistani and Saudi officials present.
A team from the Afghan government also went to the Gulf state but the Taliban refused to meet them.
A source involved in the negotiations said Pakistan had pressed for the talks to take place, and that Saudi officials had tried to persuade the Taliban members to at least shake hands or pray alongside the Afghan government representatives, but were unsuccessful.
Despite Pakistani denials, US and Afghan authorities have in the past consistently accused the country's intelligence services of backing the Taliban. In a tweet in January 2018, US President Donald Trump claimed Pakistan had given "nothing but lies and deceit" in return for American aid.
Analyst Ahmad Rashid told the BBC: "I think there has been a change in Pakistan's policy. The military and ISI [intelligence service] are trying to persuade, cajole the Taliban into meeting both the Americans and Kabul government."
Image captionThe Taliban have vastly strengthened their hand on the battlefield in recent years
Mr Rashid added: "One of the main pressures [on Pakistan] is coming not from the Americans but from the Saudis and UAE."
Both countries have recently offered Pakistan's struggling economy loans worth billions of dollars.
President Trump is thought to be considering withdrawing a significant portion of the approximately 14,000 US troops currently in Afghanistan, reportedly out of frustration at a lack of progress in the conflict.
Pakistani officials often say the country "no longer has the influence it once had" over the Taliban. But they have also insisted that they want to help create a peaceful and stable Afghanistan.
In October, Pakistan released a founding member of the Taliban, Mullah Barader from detention, reportedly to allow him to play a role in peace negotiations. Maj-Gen Asif Ghafoor, the spokesman for the Pakistani military, told the BBC last year the decision had been made because "any chance which facilitates peace, we should take that chance."
Mr Rashid said, however, that "a great amount of Taliban logistics come through Pakistan" and that it is "not clear whether those supply chains have been stopped".
One former high-ranking Taliban member expressed other doubts over the intentions of the Pakistani authorities - suggesting that in the peace talks the country was trying to propel forward members of the group sympathetic to Pakistani interests as opposed to the official political office in Qatar.
He warned that if there was too much pressure on the Taliban, negotiations might "collapse".
Who are the Taliban?
The Taliban emerged in the early 1990s following the withdrawal of Soviet troops from Afghanistan, shortly before the demise of the Soviet Union.
The militants went on to rule Afghanistan from 1996 to 2001, until they were driven from power by US-led troops following the 9/11 attacks, which the US blamed on al-Qaeda militants who were hosted by the Taliban.
The Taliban's power and reach have surged since foreign combat troops left Afghanistan in 2014.
Research carried out by the BBC in January 2018 suggested that
the Taliban were active in almost 70% of Afghanistan at the time, while being in control of 14 districts, or 4% of the country.
. we will keep supporting Afghan Taliban for peace.
