Just days after being re-elected, Russian President Vladimir Putin visited the scene in Kemerovo and blamed the deaths on "a criminal negligence, sloppiness." He did not address the rally, which went on for at least six hours.
"How could this possibly happen? What's the reason?" Putin said at a meeting with the task force dealing with the fire, according to comments distributed by his press office.
The blaze engulfed the Winter Cherry mall on Sunday, trapping dozens of parents and children inside. Witnesses reported that fire alarms were silent and many doors were locked. Some victims were children who died in a locked movie theater.
Emergency Situations Minister Vladimir Puchkov said 58 bodies had been recovered and that the rescue workers were searching for six more. Emergency officials told the Tass news agency that 41 of the victims were children.
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On Monday, investigators said a criminal investigation was launched. Putin declared Wednesday a day of national mourning.
"Most of the staff ran away and left children and parents and their children to their fate."
Many angry and grief-stricken residents of Kemerovo accused authorities of hiding the real scale of the disaster.
Natalia and Sergei Agarkov, whose two children were killed in the tragedy along with their grandmother stood on the square holding photographs of their dead loved ones.
"Masha was 10, Kostya was eight," Sergei Agarkov told Reuters. "Masha ... was really good at sports. She should have ran out, but everything was locked. I identified them yesterday. I didn't see Kostya, but recognized him by his little boots."
The impromptu protest underscored frustration with the official response to the tragedy: the local governor has not visited the site of the fire or met with the relatives.
Kemerovo's mayor asked people at the rally to nominate representatives to visit the morgue to check for themselves that the authorities were not hiding the truth about the deaths.
Deputy Governor Vladimir Chernov, the only top official who showed up at the protest, dismissed the unconfirmed reports of hundreds of deaths as rumors and said he was ready to quit if people want him to.
"Resign, resign!" the crowd chanted back.
Winter Cherry was one of Kemerovo's most popular entertainment centers for children, with an indoor skating rink, a petting zoo and trampolines.
Investigators said that emergency exits were blocked and that a security guard had not turned on the public address system to warn people to evacuate the building.
Alexander Bastrykin, the head of Russia's Investigative Committee, which handles major crimes, said that the fire alarm had not been operational for two weeks and that the security guard was detained. He added that authorities had no "reasonable" explanation for his actions.
"Most of the staff ran away and left children and parents and their children to their fate," Bastrykin said.