SEOUL: At least 146 people were killed in a crush when a huge crowd celebrating Halloween surged into an alley in a night life area of the South Korean capital Seoul on Saturday night, emergency officials said.

A further 150 people were injured in the melee in Seoul's Itaewon district, Choi Sung-beom, head of the Yongsan Fire Station, said in a briefing at the scene.

Many of the injured were in serious condition and receiving emergency treatment, the officials said.

It was the first Halloween event in Seoul in three years after the country lifted COVID restrictions and social distancing. Many of the party-goers 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. (1320 GMT).

"A number of people fell during a Halloween festival, and we have a large number of casualties," Choi said. Many of those killed were near a nightclub.

Many of the victims were women in their twenties, Choi said.

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.

Moon Ju-young, 21, said there were clear signs of trouble in the alleys before the incident.

"It was at least more than 10 times crowded than usual," he told Reuters.

Social media footage showed hundreds of people packed in the narrow, sloped alley crushed and immobile as emergency officials and police tried to pull them to free.

One woman heard on a social media post cries out in English: "Oh my God, oh my God, Jesus fucking Christ."

Choi, the Yongsan district fire chief, said all the deaths were likely from the crush in the single narrow alley.

Other footage showed chaotic scenes of fire officials and citizens treating dozens of people who appeared to be unconscious.

An unnamed woman who said she was the mother of a survivor said her daughter and others were trapped for more than an hour before being pulled from the crush of people in the alley.

A Reuters witness said a make-shift morgue was set up in a building adjacent to the scene. About four dozen bodies were carried out later on wheeled stretchers and moved to a government facility to identify the victims, according to the witness.

The Itaewon district is popular with young South Koreans and expatriates alike, its dozens of bars and restaurants packed on Saturday for Halloween after businesses had suffered a sharp decline over three years of the pandemic.

"You would see big crowds at Christmas and fireworks...but this was several ten-folds bigger than any of that," Park Jung-hoon, 21, told Reuters from the scene.

Foreigners were among those transferred to nearby hospitals.

"The area is still chaotic so we are still trying to figure out the exact number of people injured," said Moon Hyun-joo, an official at the National Fire Agency.

With the easing of the COVID pandemic, curfews on bars and restaurants and a limit of 10 people for private gatherings were lifted in April. An outdoor mask mandate was dropped in May.

Authorities said they were investigating the exact cause of the incident. President Yoon Suk-yeol presided over an emergency meeting with senior aides.