(Adds British police arrival in Moscow) By Richard Balmforth MOSCOW, Dec 4 (Reuters) - Russian Foreign Minister Sergei Lavrov said on Monday the Litvinenko affair was damaging ties with Britain, which sent detectives to Moscow as part of their investigation into the ex-KGB spy's death by poisoning. A small group of British police officers arrived at the Domodedovo airport, to begin widening their probe into the death of Alexander Litvinenko, who succumbed in a London hospital on Nov. 23 to a lethal dose of radioactive Polonium 210. Lavrov said insinuations in Britain of high-level Russian involvement in Litvinenko's death were "unacceptable", adding: "It is of course damaging our relations." 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 during a visit to Brussels that Foreign Secretary Margaret Beckett had been in touch with Moscow "and they have assured us we'll get all the cooperation necessary". Asked how long the British police would spend in Russia, a British embassy spokesman said: "They'll stay as long as it takes." Associates of Litvinenko have alleged either Kremlin involvement in his killing or that rogue elements in Russia's state security service were responsible. Before he died Litvinenko, a former Russian state security service agent who became one of President Vladimir Putin's sharpest critics in the London-based Russian emigre community, accused Putin of ordering his death. The Kremlin has strongly denied any part in the killing, and Kremlin opponents also find the theory of Putin's involvement highly improbable, noting such a high-profile killing on foreign soil could only damage him. ITALY TO PRESS KREMLIN Italy's foreign minister said he would ask Putin in Moscow on Tuesday to help the British police in their investigation. "I think that it is also an opportunity, given that Putin has decided to receive me, to tell Russian authorities that we want answers," Massimo D'Alema told reporters in Belgrade. "It's clear that I will ask Russia to offer its full cooperation to the judiciary and to the British police forces above all." The Scotland Yard detectives are likely to try to interview Russian citizens who met Litvinenko at London's Millennium Hotel on Nov. 1, the day he fell ill. Andrei Lugovoy, a former KGB agent, says he and businessman Dmitry Kovtun met Litvinenko that day at the hotel. But Lugovoy, now back in Moscow, says they discussed a business opportunity and denies anything to do with an attempt on Litvinenko's life. Alex Goldfarb, a London-based friend of Litvinenko, said the British investigators should insist on also seeing another ex-KGB agent, Mikhail Trepashkin, who had "substantive information" of use to them. Trepashkin, serving a four-year sentence in an Urals prison for divulging state secrets, alleged in a letter last Friday that the FSB, the Russian state security service, had created a hit squad to kill Litvinenko and other enemies of the Kremlin. "Mr Trepashkin has substantive information that might be of interest to investigators and his lawyers are prepared to facilitate contact with him," Goldfarb told Reuters by telephone from New York. (Additional reporting by Ingrid Melander in Brussels, Nicola Scevola in Belgrade and Mikhail Antonov in Moscow)
