At least 154 people were killed, including 26 foreigners, in a deadly stampede in South Korea, according to media reports Monday.

Thirty-three people remain in serious condition and 116 others sustained minor injuries, said Yonhap News Agency, citing officials at the Central Disaster and Safety Countermeasures Headquarters.

The foreigners killed in the deadliest stampede in South Korea's history include nationals from Iran, China, Russia, the US, Japan, France, Australia, Norway, Austria, Vietnam, Thailand, Kazakhstan, Uzbekistan and Sri Lanka, officials noted.

It marked the country’s worst tragedy since the 2014 Sewol ferry disaster that killed 304 people, most of them high school students.

Investigations are still ongoing to determine the exact cause of the tragedy.

On Sunday, South Korean President Yoon Suk-yeol declared a weeklong national mourning period following the deadly accident.

“It's truly horrific,” said Yoon, adding the “tragedy and disaster should never have happened.”

“The tragedy happened Saturday night when a massive crowd of Halloween partygoers packed a narrow 3.2-meter-wide alley in Seoul's entertainment district of Itaewon. Some of them began to fall over, causing others to fall down like “dominoes” and pile up on one another,” according to the news agency.

It was the first Halloween event in Seoul in three years after South Korea lifted many coronavirus restrictions. (Anadolu Agency)