A politically charged dispute between Moscow and London over a British cultural organization intensified Wednesday after Russia's top security agency interviewed the group's Russian employees and one of its directors was stopped by law enforcement. The British Council, which acts as the cultural arm of the British Embassy, said it was "deeply concerned" by the developments in a confrontation that has poisoned relations between the two countries, already badly strained over the killing in London in 2006 of former Russian security agent Alexander Litvinenko. It said Russia's actions had prompted the temporary closure of its St. Petersburg office. British Foreign Secretary David Miliband said that "any intimidation or harassment of officials is obviously completely unacceptable," and Britain's Foreign Office said Russia's ambassador to London was summoned for talks with British officials. A long-simmering dispute over the British Council flared this week after the organization defied Russian orders to shut its offices in St. Petersburg and the Ural Mountains city of Yekaterinburg. Russia says the offices are operating illegally. In an angry exchange Tuesday, Britain's ambassador warned that any action against the British Council would violate international law and Russia's foreign minister accused Britain of colonial-era arrogance. Then, Russia's Federal Security Service, the main successor agency of the KGB, said it was interviewing the council's Russian employees. The Federal Security Service, or FSB, said it was conducting "explanatory work" with the employees with the aim of "protecting Russian citizens from possibly being drawn into the Britons' provocative games as tools." FSB officials refused to comment further Wednesday. The British Council said its Russian staff in St. Petersburg and Yekaterinburg were "summoned for interview by the FSB at their headquarters and subsequently visited in their homes late last night by officials of the Russian Ministry of the Interior and have been called for further interviews today." The Interior Ministry is in charge of the police. Meanwhile, the director of the council's St. Petersburg office was stopped for a traffic violation Tuesday night. St. Petersburg police said Stephen Kinnock was stopped for violating a traffic sign and traffic police smelled alcohol but Kinnock refused to undergo testing. The British consul arrived later and left the scene with Kinnock. The British Council said Kinnock followed global diplomatic protocol by calling the British Consulate, which instructed him not to take the test. "Our main concern is the safety and security of both our Russian and UK staff and we are deeply concerned by both these incidents," the British Council said. Kinnock said Russian staffers were being interviewed by police Wednesday. Kinnock, who reopened the office on St. Petersburg's main avenue Monday in defiance of the Russian order, said Russia's actions had prompted the office's temporary closure but that he hoped to reopen as soon as possible. In London, Miliband described the Russian actions as an attack on the council. "We've also heard very serious reports of intimidation and harassment of British Council officials," Miliband told reporters outside Prime Minister Gordon Brown's Downing Street office. "Obviously we take that very seriously indeed. ... Any intimidation or harassment of officials is obviously completely unacceptable." He said the British Council's work in Russia was completely legal under British, Russian and international law, adding that Russia's reputation would suffer from any attack on the council's work. The dispute comes amid persistent tension over Litvinenko's death from radiation poisoning. The killing deepened tension between the West and Russia under President Vladimir Putin, a longtime KGB officer and former FSB chief who has been increasingly assertive toward Europe and the United States. Putin and FSB director Nikolai Patrushev have voiced concerns about foreign organizations operating in Russia, accused them of meddling and seeking to undermine the government. Russia has refused Britain's request to extradite Andrei Lugovoi, the main suspect in Litvinenko's poisoning, and last year Britain expelled four Russian diplomats in protest. Russia responded in kind. Foreign Minister Sergey Lavrov last month called the British Council closure order a "countermeasure" to the diplomat expulsion - proof, in British eyes, that Russia's actions are politically motivated. Russia also has been angry at Britain for years over its refusal to extradite billionaire Kremlin critic Boris Berezovsky and Chechen separatist envoy Akhmed Zakayev.