Khartoum - Russia's ambassador to Sudan, veteran diplomat Mirgayas Shirinsky, was found dead in the swimming pool at his Khartoum home on Wednesday, Sudanese and Russian officials said."The Russian ambassador died this evening at his Khartoum residence," the Sudanese foreign ministry said in a statement, without giving a cause of death."He was found dead in the swimming pool of his residence at 19:05 pm," police spokesperson Omar al-Mokhtar told AFP."Preliminary investigation shows that his death was natural," he said, as an embassy spokesperson said it apparently was caused by a heart attack.Russia's RIA Novosti state news agency reported the veteran diplomat's death, citing the foreign ministry in Moscow."We grieve to announce that on August 23 in Khartoum the Russian ambassador to Sudan, M. Shirinsky, died," it said.The press secretary at Russia's embassy, Sergei Konyashin, said there were signs the ambassador had suffered a heart attack.Decades old diplomatic and economic ties"Mirgayas Shirinsky was found in his residency in a suburb of Khartoum with signs of an acute heart attack," Konyashin told Rossiya-24 TV."Doctors were called but they didn't manage to save him."Mokhtar said Sudanese officials had taken Shirinsky's body to a morgue in the capital and were awaiting instructions from the Russian foreign ministry.A fluent Arabic and English speaker, Shirinsky had been a diplomat since 1977, the embassy said on its website.He studied at Moscow Institute of International Relations and had been appointed as ambassador to Khartoum in 2013, having previously served as ambassador to Rwanda.Shirinsky's long diplomatic career also included postings in Egypt, Saudi Arabia and Yemen.Shirinsky's "friendly yet professional approach" helped improve relations between Moscow and Khartoum, the Sudanese foreign ministry said."He used to communicate with Sudanese people from all sections and sectors of the country," a statement added.Sudan and Russia have decades old diplomatic and economic ties, and President Omar al-Bashir is expected to visit Moscow soon.