Russian President Dmitry Medvedev has ordered a sweeping check of the nation's transport services as the country observed a national day of mourning for more than 125 people believed killed in Sunday's sinking of a Volga River tourist boat.

Boats on the river blew a long blast of their horns at noon Tuesday to mourn the victims — many of them still missing. Others were killed when the aging cruise ship, the Bulgaria, listed to the right side and then sank in a storm.

Mr. Medvedev told Russian lawmakers that the accident exposed safety breaches and that the country's transportation regulations would have to be toughened. He said the 56-year-old vessel's state was “unsatisfactory” and that the “number of old rust tubs we have sailing is exorbitant.”

Transport Minister Igor Levitin said authorities are also investigating why a barge and an oil tanker passed the sinking Bulgaria without stopping to assist drowning passengers as they fought to save their lives. He said officials know the names of the captains of the other two vessels and would seek “every means” to punish them as “severely as possible.”

Rescuers have recovered more than 70 bodies so far but say there is no hope of finding anyone else alive. There were 80 survivors. Many of the victims were children who were in a playroom on the ship.

U.S. President Barack Obama expressed his condolences in a telephone conversation with Mr. Medvedev Monday.

The Bulgaria was built in 1955 in what was then Czechoslovakia. It was meant to carry 120 people, but 208 were on board when it sank during a storm near Kazan, in the republic of Tatarstan.

Survivors say the overloaded boat started listing to the right within moments of setting sail. Survivors were quoted as saying the ship sank within three minutes, giving the crew little time to take action.