In a joint statement, the 22 nations demanded that the Islamist regime respect its pledge not to harm former government or security personnel.
"We are deeply concerned by reports of summary killings and enforced disappearances", the statement says.
It follows a damning report on killings and abductions by the Islamist regime.
Released by the Human Rights Watch earlier this week, the report documented more than 100 executions and abductions of former Afghan government officials since the Taliban took control of the country almost four months ago.
It also documented the murder of 47 members of the Afghan security forces who surrendered to, or were captured by, the Taliban between 15 August and 31 October.
This is despite the regime's assurance that previous government workers would not be harmed.
The short joint statement was issued by the US and signed by the UK, European Union and a further 19 countries. It outlined their deep concerns over the report's findings and called on all cases of extrajudicial killings and enforced disappearances to be fully investigated.