Michelle Bachelet also highlighted allegations of house-to-house searches of former officials, raids on civil society groups and "increasing violence against protesters and journalists".
The Taliban are breaking their promises on women's rights and inclusivity in Afghanistan, the UN rights chief has said, as she also criticised violence against protesters and alleged reprisal killings.
Michelle Bachelet on Monday said there were "credible allegations" former members of the security forces had been killed, and some people who worked for previous administrations had been detained and later "found dead".
She also highlighted allegations of house-to-house searches of former officials, raids on civil society groups and "increasing violence against protesters and journalists".
She told the UN Human Rights Council in Geneva she was "dismayed by the lack of inclusivity of the so-called caretaker cabinet, which includes no women and few non-Pashtuns".
The announcement of the government of male loyalists last week was a key step in the Taliban's consolidation of power over Afghanistan, following a military victory that saw them oust the US-backed administration on August 15.
Notorious for their brutal and oppressive rule from 1996 to 2001, the Taliban had promised a more inclusive government this time.
However, all the top positions were handed to key leaders from the movement and the Haqqani network – the most violent faction of the Taliban known for devastating attacks.
Women 'progressively excluded'
In an update to the council on the rights situation, requested during a special session last month, Bachelet stressed that most Afghans were eager to see an end to decades of conflict and division.
"They long for peace and stability in a country where they and their children can prosper," she said.
And she highlighted promises by the Taliban to install a more moderate brand of rule including protecting women's rights.
"In contradiction to assurances that the Taliban would uphold women's rights, over the past three weeks women have instead been progressively excluded from the public sphere," she said.
Bachelet reiterated her appeal to the council to set up a "dedicated mechanism" to monitor the rights situation in Afghanistan in a bid to ensure accountability for violations.
'Respect basic human rights'
Rights groups and some countries have also voiced hope that the current council session, which lasts until October 8, will go further than the special session last month, which stopped short of ordering an international investigation into abuses in the country.
Speaking before the council on Monday, German Foreign Minister Heiko Maas for instance said his country supported "a strong mandate" for the body to monitor the rights situation in Afghanistan.
"We demand from the Taliban that they respect basic human rights, particularly the rights of women and minorities," he said, adding that it would be a "benchmark" for future engagement and aid.