Islamov, who died Wednesday, was sentenced last June to nine years in prison on charges of hostage-taking and organizing an illegal armed formation, and was being transferred to a new prison when he fell ill.
Deputy Justice Minister Yury Kalinin denied Friday that Islamov had been poisoned, saying he had suffered heart and kidney diseases. He acknowledged that when Islamov died he was suffering a severe skin allergy that is commonly a reaction to food poisoning or medicine.
Islamov's relatives told Kommersant that law enforcement officials gave Islamov some sandwiches in his cell in Krasnodar several hours before he boarded the train for a prison in Mordovia. He fell ill almost immediately but was only hospitalized in Volgograd on March 23, they said.
Islamov's lawyer told Kommersant that Islamov could not speak or move and that his hair began falling out and his skin began peeling. In the end, his heart and kidneys failed, the lawyer said.
Islamov, nicknamed "Boroda," or "Beard," was arrested in 2000 and spent three years in the Krasnodar detention center before being convicted last year.
At least three other senior rebels have died in custody since 2000, Kommersant said. Salman Raduyev and Turpal-Ali Atgeriyev died from internal bleeding, while Ruslan Alikhadzhiyev died of a heart attack, according to official autopsies.
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