At least 149 people were killed in a crush when a huge crowd celebrating Halloween surged into an alley in a nightlife area of the South Korean capital Seoul on Saturday night, emergency officials said, according to Reuters.

Another 150 people were injured in the melee in Seoul's Itaewon district. Many of the injured were in serious condition and receiving emergency treatment, the officials said.

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

Some witnesses described the crowd becoming increasingly unruly and agitated as the evening deepened. The incident took place at about 10:20 p.m. local time (1320 GMT).

"A number of people fell during a Halloween festival, and we have a large number of casualties," said a local fire chief, adding many of those killed were near a nightclub.

Many of the victims were women in their twenties, he added.

Witnesses described chaotic scenes moments before the stampede, with the police on hand in anticipation of the Halloween event at times having trouble maintaining control of the crowds.

Foreigners were among those transferred to nearby hospitals.

British Prime Minister Rishi Sunak tweeted following the incident, "All our thoughts are with those currently responding and all South Koreans at this very distressing time."

US Secretary of State Antony Blinken tweeted, "We send our thoughts and deepest condolences to the family and friends of the deceased and injured, as well as to the people of (South Korea) as they mourn this horrific tragedy."

US President Joe Biden also expressed condolences and wrote, “Jill and I send our deepest condolences to the families who lost loved ones in Seoul. We grieve with the people of the Republic of Korea and wish for a quick recovery to all those who were injured. The United States stands with the Republic of Korea during this tragic time.”

US Vice President Kamala Harris wrote, “Doug and I send our condolences to those grieving the loss of a loved one in Seoul. We stand with the people of the Republic of Korea and wish for a fast recovery to all those who were injured.”