South Korean President Yoon Suk-yeol has declared a period of national mourning following a deadly Halloween crush in the country’s capital, Seoul, as distraught relatives flocked to the city’s hospitals searching for their missing family members.

“This is truly tragic,” Yoon said in a statement on Sunday, hours after some 153 people were killed in a crowd crush in Seoul’s Itaewon district.

“The government will designate the period from today until the accident is brought under control as a period of national mourning,” he said.

The president ordered all government offices to lower their flags to half-mast, according to his office.

South Korean Prime Minister Han Duck-soo told reporters that the mourning period would last from Sunday until Saturday at Yoon’s instructions.

Fire officials said most of the victims were women and young people in their 20s and included 19 foreigners from Iran, Uzbekistan, China and Norway. A further 133 people were also injured, 37 seriously.

The stampede was believed to have been caused by huge crowds surging into a narrow downhill alley and toppling over one another at the popular nightlife district in Seoul.

 The alley, with a width of just four to six metres, was overpacked with partygoers, who moved slowly up and down the steep alley linked to bars and restaurants.

Some of them fell over on the alleyway, which got slippery because of  liquor and beverage spilled and leaflets scattered, before others toppled one after another like a domino, multiple local media reported, citing witnesses.

“People kept pushing down into a downhill club alley, resulting in others screaming and falling down like dominoes,” an unidentified witness said in a social media post.  “I thought I would be crushed to death too as people kept pushing without realising that there were people falling down at the start of the stampede,” the survivor wrote.

An estimated 100,000 people have gathered at Itaewon for the country’s biggest no-mask outdoor Halloween event since the outbreak of the Covid-19 pandemic in 2020. The country has lifted all anti-virus measures, except for an indoor mask mandate, since April.

Most of the victims were those in their late teens and 20s. Among the dead, 97 were women who are relatively not strong enough to bear the crush.

Because of the massive gatherings, police and rescuers had difficulty approaching the scene. The high death toll was also caused by the lack of paramedics required to administer cardiopulmonary resuscitation one on one for those suffering cardiac arrest and breathing difficulties.

According to some local media, the stampede occurred when some people were rushing to a bar where an unidentified celebrity visited, but it was not confirmed yet. The exact cause of the incident was under investigation.