South Korea's police chief has said their emergency response to the Itaewon crush was "inadequate" - the first acknowledgement from officials that they did not do enough to prevent it.

Amid growing calls for accountability, Yoon Hee-keun said he felt "limitless responsibility about public safety" over what happened.

He vowed a full investigation.

Interior Minister Lee Sang-min also apologised for the incident that killed 156 people and injured 152 others.

It happened on Saturday night as crowds gathered in an alley in Itaewon, a popular nightlife district in Seoul, to celebrate Halloween without restrictions for the first time since Covid.

Mr Yoon said police had received numerous calls before the accident happened, alerting them to the seriousness of the situation, but their response was lacking.

Seoul police have told the BBC the first call to South Korea's emergency number came at 18:34 local time - hours before the deadly crush reportedly began - and there were 10 more calls over the next three-and-a-half hours.

The police chief said the police response was "disappointing". They would conduct a "speedy and rigorous intensive investigation" to see if proper action was taken after receiving the calls, and if officers had reacted appropriately.

In a National Assembly meeting, Interior Minister Lee Sang-min made an apology to citizens. "It is very sad for me as a father who has a son and daughter… it is difficult to express in words how unreal this situation is, and it is difficult to accept this situation," he said.

Mr Yoon and Mr Lee's comments follow growing public demands for accountability. But other authorities have sought to portray it as an accident which could not be easily blamed on anyone.

The police earlier said they deployed more officers for this year's Halloween festivities than they did for pre-Covid parties.

One congressman on Tuesday also pointed out that because there was no main organiser for the party, there had been no special requests made to the police for crowd control and safety management.

"It's impossible to ask for legal responsibility, as nobody was responsible," said Yoo Sang-bum, who is with the ruling People's Power Party, on local radio.

Prime Minister Han Duck-soo appeared to echo this line later at a foreign media briefing, saying it was "difficult to have safety control in advance" for an incident without an organiser.

He said the government would review the issue of accountability only after a thorough investigation into the causes.

But President Yoon Suk-yeol said on Tuesday the incident revealed the importance of crowd management and a lack of research in South Korea on the subject.

"Rather than nitpicking about whether the event had an organiser or not, it's the people's safety that's important, and we need to come up with thorough measures," he said, while suggesting the use of drones and other digital capabilities to manage crowds in future events.

President Yoon had been facing mounting political pressure and plummeting ratings even before the incident. Police have said they had to redirect some of their resources to elsewhere in the city on Saturday night to manage huge protests against the government.