Russian Ambassador to Sudan Migayas Shirinskiy died Wednesday in the capital Khartoum, the Russian Foreign Ministry said in a statement.
Shirinskiy, born in 1954, was appointed to the post in 2013.
The diplomat died while swimming in the pool of his residence, according to state broadcaster Russia 24.
Shirinskiy manifested symptoms of an acute heart attack, embassy staff told the state broadcaster.
Embassy spokesman Sergei Konyashin said the staff called an ambulance but doctors were not able to save the ambassador.
The Sudanese police have ruled out the possibility of an assassination attempt, Russia 24 reported, quoting local law enforcement agencies.
Shirinskiy graduated from the Moscow State Institute of International Relations (MGIMO) and held diplomatic positions at Russia's embassies in Yemen, Egypt and Saudi Arabia.
He also served as Russian ambassador to Rwanda prior to his most recent post.
Fourth Russian diplomat to die in 2017
Though there is no evidence to suggest anything suspicious about Shirinskiy's death, he is the latest in a long line of Russian emissaries to die in the past year.
Since the start of 2017, four Russian diplomats have died. Nine have died since late 2016.
In February, Vitaly Churkin, 64, Russia's ambassador to the United Nations died of an apparent heart attack, according to the Russian mission at the UN.
Less than a month earlier, the Russian ambassador to India, 67-year-old Alexander Kadakin, died after a short illness. A spokeswoman for the embassy added there was nothing "special or extraordinary" about his death.
Two weeks before that, on January 9, a senior diplomat at the Russian embassy in Greece was found dead on the floor of his apartment. A Greek police report said he had died of natural causes.