Iranian authorities have launched a campaign of intimidation against relatives and friends of British-based Iranian journalists working for the BBC, the broadcaster said on Wednesday.
Security forces in Iran are targeting family and friends of some 10 London-based BBC staff working for the broadcaster's Persian service, director of BBC Global News Peter Horrocks said.
People had been arrested and intimidated, homes searched and passports confiscated, he wrote in a blog post.
"The relatives have been told to tell the BBC staff to stop appearing on air, to return to Iran, or to secretly provide information on the BBC to Iranian authorities," Horrocks wrote.
The intimidation increased dramatically following the broadcast of a BBC documentary about Iran's supreme leader Ayatollah Ali Khamenei around a month ago.
"Many of our Iranian employees who live in London are fearful to return to their country because of the regime's attacks on the BBC," he said.
Iran had also intensified in recent weeks its jamming of international Persian language television stations, including BBC Persian TV and the Voice of America's Persian TV, he said.
"We are seeing the levels of intimidation and bullying as well as attempts to interfere with our independence reaching new levels," Horrocks wrote.
The new claims by the BBC come after Iran announced on September 17 that six people had been arrested for allegedly gathering information for the broadcaster's Persian service.
In Wednesday's blog post, Horrocks said that "although these film-makers have never been employed or commissioned by the BBC, they are paying the price for an indirect connection to the BBC."
He called on the British and other governments to take action.
The Foreign Office in London condemned the Iranian regime and said British officials had raised the matter with their Iranian counterparts.
"We are aware of the ongoing difficulties for the BBC in Iran, which we condemn utterly," said a Foreign Office spokesman.
"The blocking of BBC Persian signals and arbitrary arrest of documentary makers not directly connected to the BBC by the Iranian regime should also be condemned.
"We have raised this issue directly with the Iranian authorities."