The United Nations said that Iran has intensified its crackdown on opponents as well as executions of drug traffickers, political prisoners, and juvenile criminals.
In a report, UN Secretary-General Ban Ki-moon also expressed concern at floggings, amputations, and the continued sentencing of men and women to death by stoning for alleged adultery.
He said in a report to the Human Rights Council that journalists, bloggers, and lawyers have been arrested or had their work impeded.
Ban called on Tehran to allow UN human rights investigators to go to Iran to assess the situation.
His 18-page report was likely to add to pressure on the UN Human Rights Council to scrutinize Iran for alleged violations.
The 47-member Geneva forum is to debate the report on March 23.