Evidence of Taliban killings, detentions and intimidation is emerging across Afghanistan ominously contradicting the hardline Islamist group’s promise earlier this week not to take revenge against its opponents.

With reports of the Taliban going door to door searching for those who worked with the former Afghan government or western countries, claims have also emerged of Taliban fighters torturing and killing members of an ethnic minority in Afghanistan after overrunning their village last month.

Amnesty International said its researchers had spoken to witnesses in Ghazni province who recounted how the Taliban killed nine Hazara men in the village of Mundarakht between the 4 and 6 of July. It said six of the men were shot, and three were tortured to death.

The brutality of the killings was “a reminder of the Taliban’s past record, and a horrifying indicator of what Taliban rule may bring”, said Agnes Callamard, the head of Amnesty International.

The rights group warned that many more killings may have gone unreported because the Taliban cut mobile phone services in many areas they have captured to prevent images from being published.

In a separate incident, Taliban fighters also killed a relative of an Afghan journalist working for the German broadcaster Deutsche Welle who they were looking for in western Afghanistan. The broadcaster revealed that three more of its journalists had also had their homes raided.

There have been reports of demonstrators being killed in several cities in recent days, and the beating and intimidation of those trying to flee the country, not least around the airport in Kabul.

Commenting on the Deutsche Welle case, Katja Gloger of the German division of Reporters Without Borders said: “Sadly, this confirms our worst fears. The brutal action of the Taliban shows that the lives of independent media workers in Afghanistan are in acute danger.”

Many Afghans fear a return to the Taliban’s harsh rule of the late 1990s, when the group largely confined women to their homes, banned television and music, chopped off the hands of suspected thieves and held public executions.

A report written by the Norwegian Center for Global Analyses said militants were also screening people on the way to Kabul airport.

“They are targeting the families of those who refuse to give themselves up, and prosecuting and punishing their families ‘according to sharia law’,” said Christian Nellemann, the group’s executive director.

“We expect both individuals previously working with Nato/US forces and their allies, along with their family members, to be exposed to torture and executions.”

With the US president, Joe Biden, suggesting on Thursday that between 50,000 and 65,000 Afghans might be at risk from the new regime, western military leaders pledged to redouble their efforts to evacuate thousands of Afghans desperate to escape Kabul’s new Taliban rulers. A Nato official disclosed that about 18,000 people had already been airlifted out.

In a sign of the new urgency, Germany said it would send two light helicopters to help evacuate citizens in the Kabul area after a German was shot and wounded driving to the airport.

However, most Afghans are unable to leave their homeland and those who may be in danger “have no clear way out”, the United Nations refugee agency said on Friday.

Shabia Mantoo, spokesperson of the UN high commissioner for refugees (UNHCR), reiterated a call to neighbouring countries to keep their borders open to allow people to seek asylum in light of what she called the “evolving crisis”.

With thousands of people still thronging the airport, the Taliban urged unity before Friday prayers, calling on imams to persuade people not to leave Afghanistan.

Criticism of the pace and conduct of the evacuation has mounted in recent days, amid images of the chaos and desperation, and evidence of the often arbitrary rules that have excluded large numbers of people who worked for western countries.

In a more hopeful sign, the US state department spokesperson Ned Price said in Washington that 6,000 people were cleared for evacuation on Thursday and were expected to board military flights in the coming hours. That would mark a major increase from previous days.

Biden is due to speak about the evacuation efforts on Friday, having faced a torrent of criticism for his handling of the troop withdrawal, negotiated by the previous Trump administration, not least the lack of planning of what was certain to be a huge rescue effort.

The Biden administration, in particular, is under pressure to expand the scope of its efforts after it was disclosed that some European forces, including an elite French police team, crossed Taliban lines and entered the city streets of Kabul to rescue civilians.

The mounting concerns about human rights violations came as an official familiar with talks with the Taliban said the group did not plan to make any decisions or announcements about the new government until after the 31 August US withdrawal date passed.

The official said the Taliban lead negotiator, Anas Haqqani, had told his ex-government interlocutors that the insurgent movement had a deal with the US “to do nothing” until after the final withdrawal date.