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 come 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.