The blaze broke out during a concert by a local pop group at the Pulse nightclub in the city of Kocani, North Macedonia.
Videos showed chaos inside the club, with people running through the smoke as the musicians urged people to escape as quickly as possible.
More than 155 people - some with severe burns - have been taken to hospitals around the Balkan country.
Health minister Arben Taravari said: "All our capabilities have been put to use, in a maximum effort to save as many lives as possible."
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Local sources revealed the ages of the victims range from 16 to 24.
Dr Kristina Serafimova, the head of Kocani General Hospital, said most of those who died were trampled in the rush to escape the flames.
Police have arrested the owner of the club and were looking for four more people.
Hristijan Mickoski, Prime Minister of the small landlocked nation, said: "This is a difficult and very sad day for Macedonia. The loss of so many young lives is irreparable, and the pain of the families, loved ones and friends is immeasurable.
image [https://cdn.magzter.com/1583517504/1742174184/articles/XlMIyX5tyKijZvo4gWsys/4474717277.jpg]
"The government will do everything in their power to slightly alleviate their pain and help t...