The UN report on human rights says secret executions are widespread in Iran [File pic: GALLO/GETTY]

Iran has criticised a report by a UN investigator that said human rights abuses in the Islamic republic appear to be increasing, blaming the US and Europe for the negative assessment of his country.

In his report to the UN General Assembly, published earlier this week, Ahmed Shaheed, the UN special rapporteur on human rights in Iran, said hundreds of prisoners have been secretly executed in the Islamic republic.

Eshagh al-Habib, Iran's deputy ambassador to the UN, said on Thursday that the report consisted of "poorly sourced, exaggerated and outdated allegations".

"Its content is absolutely unjustified, unwarranted and unacceptable for my country," he said.

"It also lacks the principles of independence, non-selectivity, impartiality."

Among the alleged abuses by the Iranian justice system that the report listed were "torture, cruel, or degrading treatment of detainees, the imposition of the death penalty in the absence of proper judicial safeguards, [and] the status of women".

According to Amnesty International, Iran had the second highest number of executions in the world last year.

The report also criticised the detention conditions of, and denial of rights to, Iranian opposition leaders Mirhossein Mousavi and Mehdi Karoubi and their wives, describing their situations as "deeply disturbing".

Karoubi and Mousavi have been under house arrest with their wives for eight months. They have not been formally charged.

They say presidential elections in 2009 were rigged.

Shaheed also said that the Iranian government had not allowed him to visit the country while making his assessment.

'Fabricated report'

Habib said the UN assembly's decision to appoint a special rapporteur in the first place was the "result of a one-sided approach and political ambition of certain countries in particularly the United State and its Europeans allies".

"The US as the main enemy ... of Iran spares no effort to manipulate the international community with fabricated and misleading misinformation," he said.

"This country is better off to look and correct the dark history and record of its own grave violations of human rights, not only at home, but also abroad."

He added that Iran had "expressed its readiness to provide all the necessary information to the Special Rapporteur [for] an impartial, balanced, nonpolitical, substantiated and well documented report".

But that was not reflected in the report, he said.

Habib urged the Third Committee to "rectify and adjust" Shaheed's report.

Meanwhile, Iran's judiciary has ordered an investigation into human rights crimes that it says have been committed by the US.

"We must open a special case for America's crimes in which there is an indictment for the crimes it has carried out in this country and other Islamic states," Ayatollah Sadeq Larijani, the country’s chief judge, was quoted as saying by the official news agency IRNA.