Rescuers scoured the wide waters of a Volga River reservoir on Monday, searching with dimming hopes for survivors after a cruise ship sank amid wind and rain.

Rescuers scoured the wide waters of a Volga River reservoir on Monday, searching with dimming hopes for survivors after an aged, overloaded cruise ship sank amid wind and rain.

Thirteen people were confirmed dead, but more than 100 remained missing.

Emergencies Minister Sergei Shoigu was quoted by Russian news agencies as saying Monday that 208 people were believed to have been aboard the Bulgaria when it sank Sunday afternoon. That's nearly 75 percent more than the 120 the boat was licensed to carry, officials said.

The ministry said 80 survivors were rescued, all of them Russian; it was unclear whether any foreigners were aboard. River cruise boats such as the Bulgaria are highly popular among Russian holiday-makers, conducting cruises ranging from a few days to two weeks.

Igor Panishin of the regional Emergencies Ministry was quoted by the state news agency RIA Novosti as saying survivors reported the ship was leaning to starboard as it made a turn and a wave washed over the deck. It sank within about eight minutes, he said.

The ship sank about three kilometers (two miles) from shore in about 20 meters (65 feet) of water, officials said.

Many children were aboard the boat, and Russian news reports quoted survivors as saying about 50 children had gathered in the ship's entertainment hall shortly before it sank Sunday afternoon.

"It happened very fast. Hatches and windows were knocked out," said Vladimir Shirybyryv, a friend of both survivors and missing people who was waiting at the river port in Kazan for word.

Based on a surviving friend's account, he said: "Everyone who survived was covered with fuel oil." One survivor told the national news channel Vesti 24 that other ships refused to come to their aid.

"Two ships did not stop, although we waved our hands," said the man in his 40s, who stood on the shore amid weeping passengers, some of them wrapped in towels and blankets. He held another man, who was weeping desperately.

President Dmitry Medvedev on Monday demanded a thorough investigation and declared Tuesday a day of mourning. He also called for a full technical assessment of the condition of all Russia's passenger vessels.

The Transportation Ministry says Russia has 1,568 registered passenger vessels — more than 100 are as old as or older than 56-year-old Bulgaria.

Emergency teams and divers from neighboring regions rushed to the site of the tragedy, 450 miles (750 kilometers) east of Moscow.

The Volga, Europe's longest river, is up to 30 kilometers (19 miles) wide in places. The river is a popular tourist destination, especially in summer months.

The Bulgaria was built in 1955 in Czechoslovakia and belongs to a local tourism company. It was traveling from the town of Bulgar to the regional capital, Kazan.

A tourism expert said the lack of partitions inside the Bulgaria made it vulnerable to breaches.

"In case of an accident these ships sink within minutes," Dmitri Voropayev, head of the Samara Travel company, told RIA Novosti.

Russia's Tourism Industry Union said the ship had not been inspected or retrofitted for years, according to the Interfax news agency.