Russia's foreign intelligence service SVR on Wednesday denied involvement in the poisoning of Alexander Litvinenko, a fierce Kremlin critic and former spy who fell seriously ill in Britain, the Interfax news agency reported. Litvinenko is in a London hospital under armed guard after what his associates claim was an assassination attempt by the Russian government. Doctors say he clearly was poisoned, but the substance used has not been identified. "Litvinenko is not the kind of person for whose sake we would spoil bilateral relations," Interfax quoted Sergei Ivanov, a spokesman for the Foreign Intelligence Service, as saying. "It is absolutely not in our interests to be engaged in such activity."