At least 59 people were killed Saturday night in the Halloween incident in Seoul’s Itaewon district, according to the Yongsan fire chief.
At least 150 other people were also injured, the chief added.
The cause of death was not immediately provided, but the chief said many people fell during the Halloween festivities, claiming casualties.
The Yonhap news agency reported that dozens of people suffered “cardiac arrest”, according to firefighters, and at least 81 people told emergency services they had “difficulty breathing”.
A total of 848 emergency forces were dispatched, including 364 firefighters and 400 police, according to the chief.
Police have cordoned off the area of the neighborhood and videos on social media show people lying in the streets.
Authorities have yet to provide exact details about the cause of the incident or the condition of the injured.