More than 100 people, many of them children, are feared dead after a tourist boat sank in central Russia.Dozens were rescued after the accident on the River Volga in Tatarstan, about 750km (450 miles) east of Moscow, but at least 199 passengers and crew were believed to have been on board.Hopes of finding survivors faded as rescuers worked through the night.The BBC’s Steve Rosenberg in Moscow said that it was a tragedy that had shocked Russia.