The Taliban and representatives of the Afghan government have restarted secret talks in the Gulf state of Qatar, senior sources within the insurgency and the Kabul government have told the Guardian.

Among those present at the meetings held in September and October was Mullah Abdul Manan Akhund, brother of Mullah Omar, the former Taliban chief who led the movement from its earliest days until his death in 2013.

The two rounds of talks are the first known negotiations to have taken place since a Pakistan-brokered process entirely broke down following the death in a US drone strike of Omar’s successor, Mullah Akhtar Mansoor.

Doha has been a centre for Taliban diplomacy since the movement was granted permission to set up an office in the Qatari capital in 2013, although that initiative became one of the many attempts to start a peace process that ultimately came to nothing following complaints from the Afghan government.

Mullah Omar’s son, Mohammad Yaqoob, is expected to soon join the Doha group, a Taliban source said, in a move that would further bolster the authority of the office.

No Pakistani official took part in either the October or September meetings, according to a member of the Taliban’s leadership council, the Quetta Shura. He said Islamabad has lost much of its traditional influence over a movement it has been associated with since it rose to power in Afghanistan in the mid-1990s.

But according to the Taliban official, a senior US diplomat was present in the Qatar meetings. The US embassy in Afghanistan declined to comment on the claim.

The Taliban official said the first meeting in early September “went positively and was held in a trouble-free atmosphere” in which Akhund sat face to face with Mohammed Masoom Stanekzai, Afghanistan’s intelligence chief.

A second meeting took place in early October, despite continued fighting between government and insurgent forces.

Recent weeks have seen the Taliban overrun Kunduz, a provincial capital, for the second time and threaten Lashkar Gah in Helmand.

Despite the unremitting violence, Kabul remains committed to trying to finding a political solution to the conflict. Late last month it finalised a peace deal with Islamist warlord Gulbuddin Hekmatyar, who had fought against the US-backed regime for more than a decade.

Although an Afghan government official confirmed Stanekzai had made at least one recent trip to Doha, both Ashraf Ghani’s spokesman and, Ismail Qasemiyar, a senior member of the High Peace Council charged with overseeing peace talks, denied any knowledge of the meetings.

The Quetta Shura member said the presence of a US official helped make the meeting possible given the Taliban’s longstanding reluctance to meet directly with the Afghan government, which it publicly lambasts as a “puppet regime”.

“Taliban believes the Afghan issue is a dispute with both the US and Afghan governments,” he said. “If these three sides can hold preliminary meetings it could create a strong base for further positive developments.”

He said Mullah Akhund was “specially dispatched by the Taliban leadership council” to Doha to underline the importance it attaches to the talks.

“His presence made the talks more notable and shows that both the military and political Taliban are on the same page,” he said.

The Taliban movement has long been divided on the wisdom of peace talks between hawkish commanders fighting in Afghanistan and some members of its leadership based in Pakistan who have favoured negotiations.

Previous attempt to find a political end to the conflict have all failed. A western security official said the recent onslaught against provincial capitals was a “strong indication that the insurgents want to pursue a military strategy regardless of the politics”.

“But we keep hearing hints and indications that various figures in the Taliban leadership want to talk as well,” he said.

The last known meeting between the two sides took place in the Pakistani hill resort of Murree in July 2015, where US and Pakistani officials were also present.

But Pakistan has been unable to orchestrate any further meetings following the death of Mansoor. A Pakistan-led “quadrilateral” process, involving Afghanistan, the US and China that was intended to presage fresh talks has also petered out.

A close aide of the Afghan president, Ashraf Ghani, said both the Taliban and the Kabul government have become deeply disillusioned with Pakistan.

“Pakistan was double dealing and insincere with the Afghan government,” he said. “We no longer think we need Pakistan and the Taliban think the same thing.”

Ghani had courted Islamabad in the hope it would use its influence to both force the Taliban to join peace talks and curtail its attacks, but violence only increased.

A western official in Kabul said a spate of arrests by Pakistani security forces of senior Taliban officials suggests Pakistan’s intelligence agencies are trying to “re-establish control over the process”.

The arrests have targeted officials chaffing under the leadership of the movement’s latest chief, Mullah Haibatullah Akhundzada, who was appointed leader in May.

The most recent arrest came on 8 October when Mullah Ahmadullah Nani was seized in Quetta, a city in south-west Pakistan.

A Quetta Shura member, Nani had special responsibility for the movement’s finances.

“Mullah Nani was on his way to the mosque near his house when masked men wearing security force uniforms arrested him and took him away,” said a senior Taliban leader.

Like many other Taliban leaders Nani lived openly in a suburb of Quetta, the capital of Balochistan, a large province bordering southern Afghanistan.

In late August Mullah Sammad Sani, a member of the Taliban’s finance and fundraising committee, was seized at a religious seminary he runs in Quetta, which a Taliban source said was sealed in front of some two hundred of his Afghan students.

During the Taliban government in the 1990s Sani served as police chief of Kandahar, Afghanistan’s second city.

“The Taliban leaders recently arrested are primarily supporters of Mullah Mansoor,” said the close aide of President Ghani. “They suspect Pakistan had a hand in Mansoor’s killing and therefore distrust it.

“The logical response is to put them away and make them less consequential, supporting instead those who are more directly under its command.”

A Pakistani intelligence official said he was unable to comment on the recent arrests.