MOSCOW: A Russian soldier has died  while serving in Syria although the cause of his death was unclear, two  people close to his family told AFP on Tuesday, but there was no  official confirmation. Vadim Kostenko, 19, from the southern Krasnodar  region, “went to Syria as a contract soldier,” a person close to the  family said by phone from Krasnodar. “He is dead,” said the person,  adding that the cause of the death was unclear and that he may not have  died in combat. The soldier is expected to be buried “in the middle  of the week,” he said, declining to be identified because of the  sensitivity of the matter. Grigory Donskikh, who served with Kostenko in  Russia and knows him well, confirmed his death but said he did not know  how he died. “He has not arrived yet,” Donskikh said, referring to  Kostenko’s body.  The defence ministry in Moscow declined to comment  when asked about Kostenko by AFP on Tuesday.