The fire which killed 64 people, many of them children, at a leisure complex was caused by "criminal negligence", President Vladimir Putin has said.

Visiting the scene in Kemerovo, Siberia, Mr Putin berated "sloppiness".

Investigators say the fire alarm was switched off and exits were blocked when the fire started on Sunday.

Interfax news agency reported that some 300 people gathered outside the local government headquarters demanding the dismissal of authorities.

The cause of the fire is not yet known, but Russia's Investigative Committee has spoken of "serious violations" at the Winter Cherry mall.

"What is happening here?", the Russian president said after laying a wreath at the scene. "This is no battle or an unexpected methane outburst in a mine."

"People, children came to relax. We are talking about demography and are losing so many people because of what? Because of criminal negligence, sloppiness."

At the scene: Relief for some

Sergei Goryashko and Elizaveta Fokht, BBC Russian

Sunday was the start of a public holiday and many children were playing upstairs at the critical moment without adults standing by to help.

Irina said that on the second floor people began shouting "Fire!". "I tried to go back up, but my path was blocked, there was a lot of people."

The parents of the birthday girl managed to rescue her and her friends. Darina was reunited with her mother on the first floor.

Darina was fretting after leaving her friend Sonya. Luckily Sonya survived, too.

How party turned into nightmare

Sunday's blaze started on an upper floor. The mall's shops, cinema and bowling alley were packed at the time.

Video on social media showed people jumping from windows to escape.

The Investigative Committee says a fire safety technician at the complex "switched off the alarm system" after being alerted about the fire.

It said a criminal investigation had begun.