A vintage double-decker passenger ship with 188 tourists on board sank on Sunday in Volga River in Russia's east-central republic of Tatarstan.
At least one person was killed in the mishap while 102 people are still missing. So far, 85 passengers have been rescued by a passing ship at the accident site, RIA Novosti reported.
The double-decker cruise ship Bolgari, which was en route from the Tatar town of Bolgar to Kazan, sank at 13:58 Moscow time (15:28 IST) o Sunday afternoon near the village of Syukeyevo in the Kansko-Ustinovsky district of the Republic of Tatarstan, nearly 750-kilometre east of Moscow.
The vintage ship was built in 1955 in the former Czechoslovakia.
Earlier, a special Ilyushin IL-76 transport aircraft with rescuers of the Central Rescue Centre left for Tatarstan.
Meanwhile, Tatarstan's police have opened a criminal case into the ship's sinking on safety violation charges, Russia's Investigation Committee spokesman Vladimir Markin was quoted as saying by Rossiya24 news channel.
The Investigations Committee's Chief, Alexander Bastrykin, has left for Tatarstan capital Kazan on the orders of President Dmitry Medvedev to establish the cause of the tragedy and find those responsible for the accident.
Russian Tourism Industry Union claimed that unlike other cruise ships used for voyages, the Volga River was not renovated.
However, the transport watchdog said the vessel was in a good technical condition with all necessary certifications.
There was "an abrupt sinking of the vessel," it said.
Dmitry Voropayev, who heads a tourism agency, said ships similar to Bulgaria don't have internal water-resistant bulkheads which makes them vulnerable to any hole in the hull.
"There were lots of children on board when the boat started to tilt on its side due to heavy rain and strong wind," reported a local TV channel.
Most of Russia's largest cities are located along the banks of Volga, a popular tourist destination especially in the summer months. It is Europe's largest river and is up to 30 kilometres wide.