Iranian authorities have asked the BBC's correspondent in Tehran to leave the country within 24 hours.
The BBC said the office would remain open despite the departure of Jon Leyne, the broadcaster's permanent correspondent there.
The request came a day after protests about the presidential election left at least 10 people dead in the capital.
Foreign media, including the BBC, are under severe restrictions, preventing reporters leaving their offices.
Jon Leyne reported for BBC radio, TV and online.
Iran has singled out Britain and the BBC in its widespread condemnation of what it calls meddling by foreign powers in its affairs.
In the days following the 12 June election, BBC Persian TV was disrupted by "deliberate interference" from inside Iran, the corporation said.
In response, the BBC increased the number of satellites that carry its BBC Persian television service for Farsi-speakers in Iran, Afghanistan and Tajikistan.
The authorities in Iran have also ordered the Dubai-based al-Arabiya TV channel to close its Tehran bureau for "unfair reporting" of the election.
"The authorities accuse al-Arabiya of diffusing news that is not necessarily fair from their point of view," said al-Arabiya's executive news manager, Nabil al-Khatib.
"The channel has not done anything that was in violation of Iranian law," Mr Khatib said in a statement on al-Arabiya's website.
In another development, the whereabouts of a Canadian journalist remain unknown.
Maziar Bahari, who works for the US news magazine Newsweek, was detained without charge on Sunday and has not been seen or heard from since.
Newsweek's editor Jon Meacham said: "We are deeply concerned about Mr Bahari's detention. As a long time Newsweek reporter he has worked hard to be balanced in his coverage."
"We see no reason why he should be held by the authorities," he added.
More than 30 journalists and bloggers have been detained since the protests began, the campaign group Reporters Without Borders says.