Alexander Pikayev, 48, a leading Russian expert on nuclear nonproliferation, was found dead in his apartment in the Maltese town of Bugibba with a blunt head wound, local media reported.
Police have ruled out murder and said Pikayev simply hit his head on a door when falling, MaltaMedia.com, a local news web site, reported Saturday. Pikayev's computer was still on when his body was discovered.
Alexei Arbatov, Pikayev's colleague at the Institute of World Economy and International Relations at the Russian Academy of Sciences, said Pikayev died Wednesday but the incident was only reported Saturday, RIA-Novosti reported.
Arbatov said Sunday that the official cause of death had not been established. He said it would be announced by Pikayev's widow, who was in Russia when her husband died but is now in Malta.
Kommersant reported that Pikayev had probably suffered a heart attack. But Nikolai Petrov, who worked with Pikayev at the Carnegie Moscow Center, told The Moscow Times on Sunday that Pikayev had not complained about his health in the months before his death.
Pikayev had worked at the Institute of World Economy and International Relations since 1984 and headed its Center for International Security in recent years. He was a consultant for the State Duma's Defense Committee from 1994 to 2003 and had worked at the Carnegie Moscow Center since 1997.
Pikayev was also a much-cited media pundit and often commented on current events in The Moscow Times.
Funeral arrangements were not immediately announced.