"Twelve people were on duty at the tanker. One person is currently missing, while two people are in a hospital," Sputnik quoted the agency's press service as saying.
"A duty officer of the Rosmorrechflot received a message about an explosion in the engine space and smoke in the accommodation space at the VF TANKER 16 in the city of Makhachkala," Rosmorrechflot said in a statement.
At the time of the incident, the tanker was near the fourth pier of the seaport in the city of Makhachkala.
"Presumably, five people were injured... Search for three people is underway," the maritime agency added.
The tanker belongs to the Volga Shipping Company, as per the initial data available.
One of the victims is in a grave condition and has sustained 95 per cent burns on his body, the regional Ministry of Health also said.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)