Four people have been detained in connection with a nightclub fire that killed at least 112 people in Russia's worst blaze in decades, as relatives began burying victims.
The club's owner, executive director, artistic director and a pyrotechnics contractor were held on Sunday pending an investigation into the blaze that occurred early on Saturday, federal investigators said.
The Investigative Committee said the suspects were ordered to be taken into custody on Sunday by the Leninsky district court on suspicion of negligence causing multiple deaths and violating fire safety rules, causing multiple deaths.
About 130 people remain in serious condition in hospitals in Moscow, St Petersburg and other cities after being airlifted to major burns units.
Doctors have said that many of the injured have more than 50 per cent burns and some are being kept alive by artificial respirators.
Witnesses say the fire was sparked by onstage fireworks that shot into the decorative twig ceiling of the Lame Horse club in the industrial city of Perm, about 1,150 km east of Moscow.
Flags flew at half mast in the city and Dmitry Medvedev, the Russian president, declared Monday a national day of mourning.
Medvedev has demanded the culprits be punished with the full force of the law, but the blaze has sparked public outrage over the authorities' failure to enforce fire safety regulations.
Mourners on Sunday expressed anger at the alleged violations, which led to a stampede as more than 200 revellers rushed towards a single narrow exit to escape the fire.
"The authorities are directly to blame, along with corruption and the criminality of the firemen," Leonid Ryabov, 51, a resident of Perm, said as he laid flowers outside the club, adding that corruption had allowed the club to ignore basic fire rules for years.
Officials said the club's managers had been fined at least twice over breaching fire regulations and called for tougher inspections to prevent a repeat of the disaster.
"When will this complacency end?" Marina Zabbarova, the head of the Russian Prosecutor-General's main investigative unit, told reporters in Perm.
She said the nightclub was not equipped with automatic fire extinguishers and fireworks should not have been used there, adding that the club's owner had tried to flee after the fire.
More than 15,000 people die each year in fires across Russia and senior officials admit that fire inspections are routinely used as a way to demand bribes from establishments rather than enforce safety rules.