South Korean President Yoon Suk-yeol ordered a period of national mourning Sunday after at least 153 people were killed in a crowd stampede in Seoul.

The crowd rush occurred during Halloween festivities as a massive crowd pushed into a narrow alleyway, crushing those in the middle of the group. Mourners laid flowers at the scene hours after first responders described carrying body after body out of the alleyway, finding few alive.

Seoul officials have received more than 350 missing persons reports following the tragedy.

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

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Seoul Halloween stampede

A man lays flowers as he mourns at the street of a deadly stampede during a Halloween festival on October 30, 2022 in Seoul, South Korea. (Photo by Chung Sung-Jun/Getty Images) (Getty Images)

Seoul Halloween Stampede

A relative of missing persons following the Itaewon Halloween stampede reacts as she waits for updates at the Hannam-dong Community Center in Seoul. JUNG YEON-JE/AFP via Getty Images)

Interior Minister Lee Sang-min confirmed that 90% of the victims had been identified as of Sunday morning, according to Reuters. 

Crowds gathered at the Hannam-dong Community Center in Seoul to learn the fate of loved ones who had been reported missing. One person reportedly fell to their knees and wept after speaking with officials.

Those killed in the incident were overwhelmingly young people, most in their 20s and some even teenagers. Halloween is a massive event for nightclubs and restaurants in Seoul, generating large crowds every year.

Officials say an additional 82 people were injured in the stampede, with 19 suffering critical injuries.

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Yoon's office ordered flags to half staff and said the government will pay for the medical expenses of the injured and the funeral expenses of those who were killed.

Seoul Halloween stampede

Emergency services at the scene of a deadly stampede during a Halloween festival on October 30, 2022 in Seoul's Itaewon district, after huge crowds of people gathered for Halloween parties, according to fire authorities. (Chung Sung-Jun/Getty Images) (Getty Images)

Seoul Halloween stampede

Oh Se-Hoon, mayor of Seoul City, speaks to members of media at the site of a deadly stampede in the Itaewon district of Seoul, South Korea, on Sunday, Oct. 30, 2022. (SeongJoon Cho/Bloomberg via Getty Images)

Chilling social media footage showed throngs of people trapped and pressed against one another in the narrow alleyway as bystanders and first responders attempted to pry people free. 

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President Biden offered his condolences to South Korea in a statement.

"We grieve with the people of the Republic of Korea and send our best wishes for a quick recovery to all those who were injured," Biden said. "The Alliance between our two countries has never been more vibrant or more vital – and the ties between our people are stronger than ever. The United States stands with the Republic of Korea during this tragic time."

Reuters contributed to this report.