South Korea’s President Yoon Suk-yeol declared a period of national mourning on Sunday after a Halloween crush killed some 151 people in a packed nightlife area in Seoul.

Yoon expressed condolences to the victims, mostly teenagers and people in their 20s, and his wishes for a speedy recovery to the many injured.

“This is truly tragic,” he said in a statement. “A tragedy and disaster that should not have happened took place in the heart of Seoul last night.”

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.

A huge crowd celebrating in the popular Itaewon district surged into an alley on Saturday night, emergency officials said, adding the death toll could rise.

Choi Sung-beom, head of the Yongsan Fire Station, said 151 deaths had been confirmed, including 19 foreigners. He told a briefing at the scene 82 people were injured, 19 of them seriously.

It was the first Halloween event in Seoul in three years after the country lifted COVID-19 restrictions and social distancing. Many of the partygoers were wearing masks and Halloween costumes.

Early on Sunday costumes and personal belongings mingled with blood spots in the narrow street. Survivors huddled under emergency blankets amid throngs of emergency workers, police, and media.

The foreigners killed included people from China, Iran, Uzbekistan and Norway.