Russian Foreign Minister Sergei Lavrov said on Monday the Litvinenko affair was damaging ties with Britain, which sent detectives to Moscow as part of the investigation into the ex-KGB spy's death by poisoning, Reuters reported. Lavrov said insinuations in Britain of high-level Russian involvement in Litvinenko's death were "unacceptable", adding: "It is of course damaging our relations." A small group of British police officers arrived at Domodedovo airport to begin widening their probe into the death of Alexander Litvinenko, who died in a London hospital on Nov. 23 from a lethal dose of radioactive polonium 210. Both Russia and Britain believe Litvinenko's death should not be politicised, Lavrov added. "If there are any questions, they should be put through law enforcement agencies," Interfax quoted him as saying. British Home Secretary (interior minister) John Reid said in Brussels that Foreign Secretary Margaret Beckett had been in touch with Moscow "and they have assured us we'll get all the cooperation necessary".