(Adds details) By Deborah Haynes LONDON, Nov 23 (Reuters) - Former Russian spy Alexander Litvinenko died in a London hospital on Thursday three weeks after he was poisoned in what friends said was a plot orchestrated by the Kremlin. Russia has dismissed the allegation as nonsense, saying it was silly to suggest the Kremlin wanted to kill Litvinenko, a critic of Russian President Vladimir Putin. The 43-year-old former spy, who had been fighting for his life in intensive care, died at 9.21 p.m. (2121 GMT), said Jim Down, a spokesman for University College Hospital. But doctors said they still did not know exactly what caused Litvinenko's death. "The medical team at the hospital did everything possible to save his life," said Down. British police said they were investigating what they called the "unexplained" death. If Moscow were found to have had a hand in his poisoning there could be far-reaching diplomatic consequences. It would be the first such incident known to have taken place in the West since the Cold War. "THE BASTARDS" "The bastards got me. But they won't get everybody," Litvinenko told friend and filmmaker Andrei Nekrasov before losing consciousness earlier this week. The comments were published in an early edition of Friday's Times newspaper. Litvinenko, who fled to Britain in 2000 with his wife and son and was granted asylum, said he fell ill after meeting two Russians at a hotel. He had been investigating the killing of Russian journalist Anna Politkovskaya, also a vocal critic of Putin, who was gunned down at her Moscow flat on Oct. 7. Britain's anti-terrorism police were called in to investigate the case after doctors determined last week his illness was caused by poison. A source in a Russian delegation with Putin, who is in Helsinki for an EU-Russia summit, told reporters: "It is a human tragedy. The man was poisoned. "But the accusations towards the Kremlin are so unbelievable, they are too silly to be commented on by the president or anyone from the Russian side," said the source, asking not to be identified. Litvinenko served in the KGB's counter-intelligence department and then the Federal Security Service's (FSB) highly secret organised crime group. The FSB is the main successor organisation to the Soviet KGB and deals with internal threats. In 1998, he turned on his former comrades and said at a Moscow news conference -- with men in masks who claimed to be Russian secret service men -- that senior FSB officers had planned to murder Russian tycoon Boris Berezovsky. He was arrested several times by his former employers at the FSB but was freed by a court and charges were dropped. Litvinenko co-authored a book in 2002 entitled "Blowing up Russia: Terror from Within", in which he alleged FSB agents coordinated apartment block bombings in Russia that killed more than 300 people in 1999. Russian officials blamed the bombings on Chechen separatist rebels.
