Russian state broadcaster Russia Today's bank accounts have been frozen in the UK.
RT's editor-in-chief Margarita Simonyan tweeted to say: "Our accounts in the UK have been closed. All accounts. 'The decision is not subject to revision'.
She added: "Long live freedom of speech!"
What is Russia Today?
RT, originally known as Russia Today, is a television network and news website funded by the Russian government.
It is run by the Kremlin in Moscow and has been accused of disseminating Russian propaganda and having anti-Western leanings in its reports.
RT says it offers "an alternative perspecive on major global events" with a "Russian viewpoint".
What are the past controversies surrounding RT?
The broadcaster was previously sanctioned by Ofcom for biased or misleading reports on the conflicts in Ukraine and Syria.
It had accused the BBC of staging a chemical weapons attack conducted by the Assad regime in Syria for a news report.
Earlier this year the network was accused of censoring footage of Russian jets in Syria to cover up the use of incendiary bombs.
The clip was later reinstated, with RT saying it had been removed over concerns for a pilot.
Why have its bank accounts been frozen?
It is currently unclear why NatWest and the Royal Bank of Scotland Group have closed RT's bank accounts.
In a letter to RT's London Office, NatWest said: “We have recently undertaken a review of your banking arrangements with us and reached the conclusion that we will no longer provide these facilities."
The broadcaster's editor suggested it "may have something to do" with potential sanctions against Russia by the UK and US.
“We have no idea why it happened, because neither yesterday nor the day before yesterday, nor a month ago, nothing special happened to us, nobody threatened us in any way," Margarita Simonyan told the RBK business news website.
"Hypothetically, this may have something to do with new British and American sanctions against Russia, which may be announced soon. It may not. Our legal department is dealing with the issue now."
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies