The statements were made during a meeting of the UN Human Rights Council on the situation in Iran.
"I call on the Iranian authorities to rethink, to step back, and to put an end to their brutal repression, including summary trials and disproportionate sentences," said UN human rights chief Volker Türk.
He highlighted the use of live ammunition by Iranian security forces and referred to the numerous reports of peaceful protesters being shot dead in the streets. Türk also called on Iran to release all arbitrarily detained people and not to impose any death sentences.
The Human Rights Council also decided that independent investigators should conduct an in-depth examination of the situation.
