A diplomatic row between Russia and the UK has intensified after Britain reopened two regional cultural offices, defying a Moscow order to shut them.
Two British Council offices reopened despite an order to stay shut
Russia accused Britain of "intentional provocation" and said it would refuse new visas to British Council staff.
The UK ambassador, who was summoned by the Russian foreign ministry, said the offices will remain open.
They were ordered to shut last month in a continuing dispute over ex-KGB agent Alexander Litvinenko's death in London.
The offices that reopened after the holiday break are in St Petersburg and the Urals city of Yekaterinburg. The ban does not apply to the British Council's Moscow office.
A statement on the Russian foreign ministry's website said: "Russia views such actions as an intentional provocation aimed at inflaming tensions in Russian-British relations.
"The Russian side will not issue visas to new employees sent to work in the [British] consular offices of St Petersburg and Yekaterinburg to carry out British Council work."
Emerging from his brief meeting in the Russian capital, British ambassador Sir Tony Brenton said he had told Vladimir Titov, the deputy foreign minister, a "serious disagreement" existed between the two countries.
Mr Titov had handed him "a long piece of paper setting out the Russian legal view on the work of the British Council", he said.
The diplomat said he had replied that "the British Council is working entirely legally, that it will continue therefore to work, that any Russian action against it would be a breach of international law".
He said he had told Mr Titov: "It's also the case that we have a huge number of other subjects where Russia and the UK need to work together and we need to be quite careful to prevent this situation infecting all the other pieces of business."
Nov 2006: Alexander Litvinenko dies in London
May 2007: UK accuses ex-KGB agent Andrei Lugovoi of murder
July: Russia refuses British request to extradite Mr Lugovoi
July: UK expels four Russian diplomats
July: Russia expels four British embassy staff
Dec: Russia orders British Council to shut two offices
Jan 2008: British Council re-opens both offices
BBC Moscow correspondent Richard Galpin says Russia has clearly been angered by the British Council defiance.
The escalating diplomatic crisis is now coming to a head and it is not clear if either side is willing to back down, he says.
The British Council, which aims to promote cultural and educational ties, has been accused of violating Russian tax rules.
Council chief executive Martin Davidson said it would continue talking to the Russians in the hope of continuing its "enormously valuable" work.
He told the BBC: "We know ordinary Russian people believe it is of real value to them, as well of course to us here in the UK, to have that relationship with Russia."
Opinion about the Council was divided on the streets of St Petersburg on Monday.
Tatyana Mokhova said: "I think they should continue working, because such offices are needed to develop culture in society."
But Sergey Ermoshkin said: "Any reasonable person understands that British intelligence is legally working under cover of such organisations."
The row came on top of ongoing tensions over the death of former KGB officer Litvinenko in London in November 2006. He had been given a fatal dose of radioactive polonium 210.
The UK wants Russia to hand over businessman Andrei Lugovoi, whom UK investigators suspect of murdering Mr Litvinenko.
When Russia refused to extradite Mr Lugovoi, Britain expelled four Russian diplomats and Moscow followed suit.
Russian officials have described the action against the British Council as a retaliatory measure.