"The cause may have been the dispersal of a stinging substance, the young people fled and trampled over each other. Sadly, six people died and dozens are injured," the fire service said in a statement on Twitter.
The victims include five people under the age of 18 -- three girls and two boys - and an adult woman who accompanied her daughter to the concert, media reports say.
They said 12 of the injured were in serious condition.
Witnesses said people were crushed to death after falling from a small wall as they attempted to flee.
The accident happened around 1am (0000 GMT).
"We were dancing and waiting for the concert to start when we smelt this pungent odour," a 16-year-old boy who was taken to hospital told the media.
"We ran to one of the emergency exits but we found it blocked, the bouncers told us to go back."
In 2017, a woman died and 1,500 were injured in a crush during the broadcast of a Champions League football match final in Turin when rumours of a bombing sparked panic.
Eight people were arrested on suspicion of causing the scramble by dispersing an irritating substance in a bid to steal from the crowd.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)