LONDON, England, July 17, SPA -- UK Prime Minister Gordon Brown's new government ordered the expulsion of four Russian diplomats Monday over the Kremlin's refusal to extradite the key suspect in the fatal poisoning of a former KGB spy -- Britain's first use of the sanction in more than 10 years. Russia quickly threatened retaliation, marking a new low point in Britain's relations with Moscow under President Vladimir Putin, the Associated Press reported. Alexander Litvinenko died November 23 in a London hospital after ingesting radioactive polonium-210. In a deathbed statement, the 43-year-old accused Putin of being behind his killing. British prosecutors have named Russian businessman and former KGB agent Andrei Lugovoi as the chief suspect. Litvinenko said he first felt ill after meeting Lugovoi and business partner Dmitry Kovtun at a London hotel. But Russia has refused to extradite Lugovoi, saying its constitution prevents that. Brown, speaking in Berlin, said, "I have no apologies for the action that we have taken, but I do want a resolution of this issue as soon as possible." "When a murder takes place, when a number of innocent civilians were put at risk ... when an independent prosecuting authority makes it absolutely clear what is in the interest of justice and there is no forthcoming cooperation, then action has to be taken," the British leader said. Foreign Secretary David Miliband told lawmakers in the House of Commons that "the Russian government has failed to register either how seriously we treat this case or the seriousness of the issues involved, despite lobbying at the highest level and clear explanations of our need for a satisfactory response." Russia immediately threatened to retaliate. "London's position is immoral," Russian Foreign Ministry spokesman Mikhail Kamynin said. "They should understand well in London that the provocative actions conceived by British authorities will not go unanswered and cannot fail to produce the most serious consequences" for bilateral relations, he said. Lugovoi said Monday the British decision "once again confirms that the Litvinenko affair had a political subtext from the very beginning," the Interfax news agency reported. Russia formally rejected an extradition request a week ago, and British prosecutors then spurned an offer from Moscow to try Lugovoi there.--SPA www.spa.gov.sa/468066