MOSCOW, Aug 31 (Reuters) - BBC journalist Sarah Rainsford left Russia on Tuesday after Moscow abruptly refused to extend her permission to work in what it said was a tit-for-tat row with Britain over the treatment of foreign media. Russian authorities earlier this month told Rainsford, one of the British broadcaster"s two English-language Moscow correspondents, to leave the country in retaliation for what it called London"s discrimination against Russian journalists working in Britain. Russian authorities accused London of mistreating a Russian journalist working for the state TASS news agency in London who they said was forced to leave in 2019 after his visa was not extended without explanation. They said they had tried and failed to get Britain to remedy the situation before deciding to retaliate in kind. The BBC has called the expulsion of Rainsford a "direct assault on media freedom" and the British government had without success urged Russian authorities to reconsider their decision. Rainsford, who has said she was devastated by the move, posted pictures on Twitter on Tuesday from a Moscow airport before she boarded a flight out of the country. In a farewell report, the BBC aired footage of Rainsford first being denied entry to Russia on Aug. 10 and being told she was being denied a visa "for life." Rainsford is seen saying she had been told by Russia"s FSB security service that she had been designated a national security threat. She said she had later been allowed to enter Russia in order to pack up her life there. Her departure, a de facto expulsion, follows a crackdown before parliamentary elections in September on Russian-language media at home that the authorities judge to be backed by malign foreign interests intent on stoking unrest. "At a time when Russia is seeing enemies all around it really feels like I"ve been added to the list," said Rainsford. Russia"s foreign ministry has made clear it will not allow the BBC to send her back or to replace her with someone else until Britain gives a visa to a Russian journalist it wants to be able to work in London.