A Russian cruise ship which sank in the Volga river on Sunday left port listing to starboard with a broken engine, local investigators said on Monday.

Up to 120 people are feared to have died on the cruise ship Bulgaria, after the Emergencies Ministry confirmed that the ship was carrying 208 people, including 59 children, instead of the maximum 120 allowed by safety rules.

The twin-deck Bulgaria, built in 1955, sank on Sunday at 01:58 PM Moscow time (09:58 GMT) near the village of Syukeyevo in the Kansko-Ustinovsky district of the Republic of Tatarstan.

"During their initial investigation it was established that on departing for Kazan, the ship had a malfunction of the port engine, however, the vessel set out on the voyage," the local transport investigation committee said.

"It was also established that departing on July 10 at 11.15 Moscow time (07.15 GMT) en route from the town of Bolgar to Kazan, the ship had a list to starboard, which may be due to sewage tanks not being emptied, fuel available only in the right tank, and so on," the committee said.

Witnesses said the vessel rolled on its right side and sank in eight minutes. The ship may have flooded rapidly due to open portholes and the list to starboard, the Investigation Committee Central Department said.

The vessel passed a regular technical inspection on June 15 this year and was certified fit for use, the Transport Ministry said in a statement.

A total of 79 people were rescued, while over 100 are still missing and 24, including a child, have been found dead, the Russian Emergencies Ministry said on Monday.

A criminal case has been launched into possible safety violations related to the ship's sinking, Russia's Investigative Committee said in a statement.

The Bulgaria may not have had enough life-saving equipment for all those on board. The ship had life-rafts for 120 people, and two lifeboats for 36 people, as well as 165 life-vests for adults and 12 for children, the ministry said.

Russian President Dmitry Medvedev expressed condolences in his micro blog Twitter to the relatives of those who died on board the Bulgaria.

Medvedev has declared Tuesday, July 12, a day of mourning for those who died on board the vessel.