Iran on Wednesday condemned a report by a United Nations expert that accused the country of "atrocity crimes" against minorities and killings in the 1980s.

Javaid Rehman, the UN's independent special rapporteur on the rights situation in Iran, on Monday called for a probe into allegations Iran committed summary, arbitrary and extra-judicial executions in 1981-1982 and in 1988.

He said in a statement, after releasing a report with his detailed findings, that the actions "amounted to crimes against humanity of murder and extermination, as well as genocide".

Iran's foreign ministry spokesman Nasser Kanani dismissed the report as an attempt by Tehran's "enemies to tarnish the image of the Islamic republic".

"The claims lack any legal basis and are completely rejected," said Kanani, accusing Rehman of "abusing his position" and spreading "false news".

In his report, Rehman said there should be "no impunity for such gross human rights violations, regardless of when they were committed".

"The Iranian regime and its leaders should not be allowed to escape the consequences of their crimes against humanity and genocide," he added.

The expert, whose mandate ends on July 31, said that "the targeting and victimising of religious, ethnic and linguistic minorities and political opponents continued with complete impunity during, and since, the first decade of the establishment of the Islamic republic in 1979".

He highlighted in particular attacks on the Bahai -- Iran's largest non-Muslim minority -- which he said was "targeted with genocidal intent and persecution".

In response, Kanani said: "Iran reserves its legal right to protest this wrong process in some human rights institutions".