Russian Prime Minister Vladimir Putin is blaming “irresponsibility” and “greed” for the recent sinking of an aging riverboat that killed at least 113 people.

Prime Minister Putin made an unannounced visit Thursday to Kazan, the central Russian city from which the ill-fated Bulgaria had departed and was sailing back to on Sunday when it listed to the right and sank in the Volga River during a thunderstorm. Mr. Putin laid down crimson roses at the river port.

The death toll from Russia's worst river disaster in three decades is expected to increase. Twenty people are still missing and presumed dead. Officials said they have pulled 113 bodies from the river — 27 of them children.

The tragedy has angered many in Russia. In televised remarks, Mr. Putin blamed the accident on a “crude violation of basic safety requirements.” He said it is “horrible that we have to pay such a toll for this irresponsibility, such complacency, such greed.”

Mr. Putin said his government needs to analyze the regulations for river transportation and adopt strict controls.

Authorities have arrested four people connected to the accident — the director of the company that leased the 56-year-old boat, a river transport inspector and the captains of two vessels that allegedly passed the sinking boat without stopping to help drowning passengers trying to save their lives.