The ages of the victims were not immediately given and it was not immediately clear how many people were inside when the stampede erupted or the club's maximum capacity.
Teenagers panicked before a rap concert at a jammed Italian disco, setting off a stampede that killed five of them and a mother who had brought her daughter to the event, authorities and survivors said. It quoted one teenager as saying that the emergency exit was blocked.
Local officials said witnesses reported seeing a hooded man spray a substance like pepper spray or tear gas into the crowd. "We were told that about 60 people had been taken to hospitals", the spokesperson said.
A pile of abandoned shoes testified to the chaos of the stampede, with survivors and the bereaved weeping outside the nightclub as emergency vehicles tended to the injured, local newspaper Ancona Today reported. Breaking through the barrier, bodies began to fall over, trampling and falling on top of one another. State radio said most of the dead had their skulls crushed in the melee.
Local media report around 120 people were injured, including 35 who were taken to hospital.
Local media reported that numerous victims were trampled, as the venue was packed at the time of the incident.
Hundreds had been waiting to see popular rapper Sfera Ebbasta perform when someone in the club sprayed an "irritant substance", leading to a stampede, Italy's civil protection agency said.
He said that when rescuers arrived, all the doors of the discos were open.
"We will find those responsible for these six broken lives, those who out of malice, stupidity or greed have turned a party night into a tragedy", he added.
Italian President Sergio Mattarella promised to work tirelessly to determine "any responsibility and negligence".
"Citizens have the right to safety wherever they are, in workplaces as well as places of entertainment", Mr Mattarella said in a statement. "One can not die this way".
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