South Korea is mourning the deaths of more than 153 people, mostly in their 20s and 30s, who were crushed after a huge Halloween party crowd surged into a narrow alley in Seoul.
The Ministry of the Interior and Safety said the death count could further rise as 37 of the 133 other injured people were in serious conditions.
Ninety-seven of the dead were women and 56 were men. More than 80 per cent of the dead are in their 20s and 30s, but at least four were teenagers.
At least 20 of the dead are foreigners including one from Australia, one American and others from China, Russia, Iran and elsewhere.
Witnesses said the crowd surge on Saturday night in the Itaewon area caused "a hell-like" chaos as people fell on each other "like dominoes."
Some people were bleeding from their noses and mouths while being given CPR, witnesses said, while others clad in Halloween costumes continued to sing and dance nearby, possibly without knowing the severity of the situation.
"I still can't believe what has happened. It was like a hell," said Kim Mi Sung, an official at a nonprofit organisation that promotes tourism in Itaewon who performed CPR on 10 people who were unconscious before nine of them were declared dead.
An estimated 100,000 people had gathered in Itaewon for the country's biggest outdoor Halloween festivities since the pandemic began. The South Korean government had eased COVID-19 restrictions in recent months.
Authorities said thousands of people have called or visited a nearby city office, reporting missing relatives and asking officials to confirm whether they were among those injured or dead after the crush.
South Korean President Yoon Suk Yeol declared a one-week national mourning period on Sunday and ordered flags at government buildings and public offices to fly at half-staff.
"This is really devastating. The tragedy and disaster that need not have happened took place in the heart of Seoul amid Halloween (celebrations)," Yoon said during the speech.
In an interview with news channel YTN, Hwang Min-hyeok, a visitor to Itaewon, said it was shocking to see rows of bodies near the hotel. He said emergency workers were initially overwhelmed, leaving pedestrians struggling to administer CPR to the injured lying on the streets. People wailed beside the bodies of their friends, he said.
World leaders offered condolences, including British Prime Minister Rishi Sunak.
"All our thoughts are with those currently responding and all South Koreans at this very distressing time," he tweeted.
Jake Sullivan, the US national security adviser, tweeted that reports of the disaster were "heartbreaking" and said Washington "stands ready to provide the Republic of Korea with any support it needs."
The last South Korean disaster this deadly also hit young people the hardest. In April 2014, 304 people, mostly high school students, died in a ferry sinking. The sinking exposed lax safety rules and regulatory failures. It was partially blamed on excessive and poorly fastened cargo and a crew poorly trained for emergency situations.
Saturday's deaths will likely draw public scrutiny of what government officials have done to improve public safety standards since the ferry disaster.
This was the deadliest crushing disaster in South Korean history.
It was also Asia's second major crushing disaster in a month. On October 1, police in Indonesia fired tear gas at a soccer match, causing a crush that killed 132 people as spectators attempted to flee.