He vowed the government would make the "necessary changes" to prevent such an accident from happening again.

At least 154 people died and more than 80 were injured in the incident on Saturday night during a Halloween festival in the nation's capital.

Tens of thousands of party-goers had crowded into narrow streets and alleyways of the South Korean capital's popular Itaewon area, a major leisure, and nightlife district, on Saturday for the first virtually unrestricted Halloween festivities in three years.

Many of the victims were in their teens and dressed in costume.

The country is now observing national mourning for the victims.

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Chaos had erupted when people poured into one particularly narrow and sloping alley, even after it was already packed, witnesses said.

A stunned Seoul was just beginning on Monday to understand the huge scope of the surge that killed mostly people in their 20s and 30s.

The Ministry of the Interior and Safety said it expected the death toll to rise on account of the number of injured people in serious conditions.

"The government will undertake a thorough investigation into what caused this accident and do its best to make necessary institutional changes so that such an accident is not repeated," Mr Han said as government officials met on the disaster.

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"Identification has been completed for all of the 154 deceased except one, and I believe it is time for follow-up measures such as funeral procedures to be carried out in earnest," Han said. "We will do our best to provide necessary support by reflecting the opinions of the bereaved families as much as possible."

President Yoon Suk-yeol designated Itaewon a disaster zone.