Mai Anh Huynh, chairman of the Phu Quoc District people's committee, affirmed that the two bodies found at the scene are Russians, and the nationalities of the two foreigners injured have not been determined.
An explosion was heard from a wooden homestay house in Nguyen Thi Dinh Street at around 3 a.m, and flames shot up soon after, local witnesses said.
Many people were seen trying to get out of the house and some were severely burned.
Firefighters put the fire out in three hours. Local authorities are investigating the fire.
Phu Quoc Island is a tourism hotspot in Kien Giang Province, southern Vietnam.