Four UN experts on Wednesday accused Tehran of death threats against journalists for the BBC and other broadcasters, and their families.
The special rapporteurs, independent experts who do not speak for the UN but report their findings to it, voiced their alarm and urged the Iranian authorities to stop threatening reporters.
They said the journalists "faced threats, criminal investigations, unlawful surveillance, freezing of assets, defamation and harassment by Iranian authorities".
"Several journalists have also been targeted for going public about the harassment and seeking protection from the UN."
The BBC said the"recent escalation in harassment" of its Farsi service staff and their families coincided with a crackdown on dissent in Iran.
It said "express threats" had been made "by state officials" towards the safety of BBC journalists outside Iran.
The BBC said that Rana Rahimpour, a journalist with its Farsi service, told of receiving a message threatening that she, her husband and their children would be assassinated within a month, while there were also threats against her elderly parents living in Iran.
The UN rapporteurs warned Tehran that such actions could breach Iran's human rights obligations under international law.
They urged the Iranian government to "cease the intimidation, harassment and threats, including death threats, against BBC and other journalists working outside Iran for Farsi-language news outlets, as well as reprisals against their family members in Iran".