MOSCOW — Russia yesterday ordered a British cultural organization to suspend all its operations outside Moscow at the beginning of 2008, the latest move in a long-running dispute.

Russian officials accused the British Council, a nongovernmental organization that acts as the cultural department of the British Embassy, of operating illegally in St. Petersburg and Yekaterinburg. Russian officials, who have long claimed the council is a for-profit organization subject to taxation, made the announcement at a time when relations between the two countries are at a low point. “We think this is a very serious and illegal measure,” Foreign Secretary David Miliband of Britain said. He said Burma and Iran were the only two countries in which the British Council was not allowed to operate.

“I very much hope that the announcement today from the Russian government does not signal that they are taking steps down that road because it is a deeply unwholesome company with which to be,” Mr. Miliband said. A Russian Foreign Ministry spokesman, Mikhail Kamynin, said in a statement that British Council operations in St. Petersburg and Yekaterinburg violated the Vienna Convention on Consular Relations. Ambassador Anthony Brenton of Britain was told yesterday that the branches in those cities must suspend operations January 1, the ministry said.

Britain denied the allegation. “Under the Vienna Convention, the British Council is permitted to run services which benefit Russians as well as Britain,” a senior British Foreign Office official told the Associated Press in London, speaking on condition of anonymity in line with ministry practice.

“It will be very disappointing if they go ahead with this threat,” the official said.

In Moscow, a British Embassy spokesman said the regional offices abide by a British-Russian cultural agreement signed in 1994.

“Any action against the British Council would constitute a serious breach of international law and would deprive Russians of cultural and educational resources,” he said on condition of anonymity.

Natalia Minchenko, marketing director for the British Council’s main Moscow office, said they had “no plans to shut down” the St. Petersburg and Yekaterinburg offices.

British-Russian relations have been under increasing strain.

Britain this year called for Russia to extradite Andrei Lugovoi, its suspect in the 2006 killing in London of dissident former security agent Alexander Litvinenko. Russia says its constitution prohibits it from doing so.

Russia is furious at Britain for refusing to extradite a fierce Kremlin critic, tycoon Boris Berezovsky, and a Chechen separatist envoy, Akhmed Zakayev. Both men have been granted political asylum in Britain.

In July, Britain expelled four Russian diplomats in protest at the refusal to extradite Mr. Lugovoi. Russia countered by ordering four British diplomats to leave. Foreign Minister Sergey Lavrov of Russia, in an interview with BBC television, suggested the Russian order on the British Council was at least in part a response to British moves in the dispute over Mr. Lugovoi.

“The British government undertook some actions and inflicted what I would call systemic damage to our relations, so we have to retaliate,” Mr. Lavrov said. He said the expulsion of diplomats was “inevitably calling for retaliation.”

The order also demonstrates Russia’s general suspicion of foreign nongovernmental organizations. Many officials accuse them of meddling in the country’s politics and even of attempting to organize opposition movements to try to undermine the government.

“I know for sure that the British Council’s projects have been closely associated with education programs rather than politics,” a prominent Russian human rights activist, Lev Ponomarev, was quoted as saying by the Interfax news agency.