President Dmitry Medvedev demanded that Russia tighten its notoriously lax fire codes after the deadliest blaze since the Soviet era killed at least 107 people celebrating in a nightclub with a decorative twig ceiling and single exit.
About 130 people were injured, dozens critically, when onstage fireworks set the ceiling of the Lame Horse nightclub ablaze soon after midnight on Saturday, witnesses and officials said.
Many victims were trapped in a panicked crush for the exit as they attempted to escape the flames and thick black smoke.
Authorities quickly arrested two registered co-owners of the club, its managing director, and two other suspects. One other suspect was injured in the fire and remains in critical condition.
Officials said club managers ignored repeated demands from authorities to change the interior to comply with fire safety standards.
Emergency Situations Minister Sergei Shoigu told Mr Medvedev by videoconference from Perm that the club managers violated the law by running the fireworks display that triggered the fire.
He said club managers had been fined twice in the past for breaking fire safety regulations, which he did not specify.
Russian clubs and restaurants often cover ceilings with plastic insulation and a layer of willow twigs to create a rustic look, one of many uses of combustible materials in buildings by businessmen who bribe officials to look the other way.
The Lame Horse's managers had been scheduled before the fire to report tomorrow on their progress fixing the flaws.
"They have neither brains, nor conscience," Mr Medvedev said. "They must face the maximum punishment."
He declared a national day of mourning for tomorrow.
Mr Medvedev demanded that politicians draft changes to toughen the criminal punishment for failing to comply with fire safety standards.
Enforcement of fire safety standards is infamously poor in Russia and there have been several catastrophic blazes at drug-treatment facilities, nursing homes, apartment buildings and nightclubs in recent years.
The nation records up to 18,000 fire deaths a year, several times the per-capita rate in the United States and other Western countries.