Some 100 people were missing after a tourist boat sank in Russia's Volga river on Sunday, killing at least one person, emergency services officials said.
The authorities said 84 people were rescued and two people died.
The boat was heading to the Tatarstan regional capital, Kazan, 800 km east of Moscow, when it sank about 3 km from shore in 20 metres of water, officials said.
A survivor said the two-decked, 56-year-old riverboat sank fast in a thunderstorm after listing onto its side, the Interfax news agency reported.
Rescuers searched choppy waters in a broad stretch of the river as daylight faded and survivors, rescued by a passing craft, greeted anxious relatives on shore.
The boat "leaned onto its right side, turned over in literally three minutes and went to the bottom", Interfax quoted a man who was rescued by the passing boat as saying after it docked in Kazan.
"There was thunder and heavy rain at the time. There are very many dead," the man, who said his wife and son drowned, was quoted as saying.
The man, whose name was not given, said about 30 children had gathered in a playroom near the bow minutes before the boat sank. "I'm afraid many of them dead," Interfax quoted him as saying.
Cruises on the Volga, which cuts through the heart of Russia and drains into the Caspian Sea, are popular among Russians as well as foreigners.
The cause of the sinking of the boat, the Bulgaria, was unclear, an Emergency Situations Ministry spokesperson said. It was built in 1955 in Czechoslovakia.