He said the government "will thoroughly investigate the cause of the incident and make fundamental improvements to ensure the same accident does not occur again in the future".
"My heart is heavy and it is difficult to contain my sorrow," he added, before he visited the scene of the disaster and spoke to emergency workers.
While Halloween isn’t a traditional holiday in South Korea, where children rarely go trick-or-treating, it’s still a major attraction for young adults, and costume parties at bars and clubs have become hugely popular in recent years.
Itaewon, near where the former headquarters of U.S. military forces in South Korea operated before moving out of the capital in 2018, is an expat-friendly district known for its trendy bars, clubs and restaurants and it’s the city’s marquee Halloween destination.
VIEW PHOTOS | South Korea's worst-ever stampede
Rumours galore
In the absence of an immediate official explanation, rumours have exploded online.
Some users have speculated the stampede could have been triggered by a gas leak or a fire at one of the clubs, others claim the cause could have been a celebrity sighting. Online users also floated the possible use of drugs, with photos of purported "drug candies" allegedly handed out at the event circulating on Twitter.
Police have so far found no evidence of any of this. Experts, instead, point to policing and crowd control failures.
(The video below can be disturbing)