South Korea: How the Halloween tragedy unfolded

After more than 150 people died in a deadly crush in Seoul on Saturday night, the BBC looks at how the tragedy unfolded.

Gathering crowds

Thousands of mainly young people had converged in Itaewon in the centre of the South Korean capital of Seoul.

It's a lively party spot with many narrow streets and alleys filled with bars and restaurants.

Some accounts say more than 100,000 had descended on the area that evening.

The neighbourhood is served by Itaewon metro station, and videos on social media show streams of people arriving to celebrate Halloween from early evening on Saturday.

Nuhyil Ahammed, 32, was in the crowd. The IT worker from India lives nearby and had been to Halloween parties in Itaewon before, but says things were very different this year.

Large crowds gathered in Itaewon a few hours before the crush

"It was crazy," he told the BBC. "From 5pm there were too many people on the streets. So I was thinking, what's it going to be like from seven or eight?"

Around this time, social media messages were being posted online with people saying that the streets of the district were so crowded they felt unsafe.

The first call to police from Itaewon came at 18:34 local time - several hours before the deadly crush took place in an alley off the main road.

"That alley is really dangerous right now people going up and down, so people can't come down, but people keep coming up, it's gonna be crushed. I barely made it to get out but it's too crowded. I think you should control it," the caller said.

The police officer asked if the caller meant that people weren't flowing well, that "they get crushed and fall, and then there's going to be a big accident?"

Yes, the caller responded - "this is so chilling right now".

The police officer told the first caller they would send someone "to go and check it out" - but no significant reinforcements were sent for hours.

South Korea's police chief has said their emergency response was "inadequate"

Authorities said they had 137 officers on the ground at Itaewon that night. But they were clearly outmatched by the many thousands that flocked to the area.

Videos show people converging into a narrow alley next to the Hamilton shopping mall where the worst overcrowding was reported.

There were at least ten more emergency calls from the area in the next three and a half hours, for which the police have taken the unusual step of releasing transcripts.

The next few calls started coming in about two hours later, from 20:09 onwards.

Callers described seeing people stumbling after they were pushed, and getting injured. At 20:53, one caller described a harrowing situation near a nightclub on the alley.

"I feel like I am going to get crushed… many people are being crushed… it is chaos." They repeatedly begged "please help us".

The caller was reassured that police would be sent to the scene. But records show they were not, and out of the 11 phone calls made to police, they only mobilised officers for four of them.

The police did not dispatch anyone for in response to calls made from 21:07 onwards - the hour leading up to the crush.

The crush

In the last call at 22:11 - one of the briefest made - the caller said: "It feels like people can get crushed here."

Minutes later, the deadly crush began.

At about 22:15 a number of people on the sloping pathway fell over. Crowds pressing from both ends of the alley made it impossible to get out.

Social media footage shows some people trying to climbing up the sides of the buildings to escape.

At 22:24, fire authorities say they received reports that 10 people were pushed down under the crowd and experiencing breathing difficulties.

At 22:27, the first four ambulances were dispatched, followed by six more a few minutes later, according to the authorities.

The clogged streets made it difficult for emergency workers and ambulances to reach the area

"People began pushing from behind, it was like a wave - there was nothing you could do," Mr Ahammed said, who found himself caught up in a huge crowd.

"People were suffocating, screaming, getting squeezed, falling... there were just too many people"

By 23:00, 30 more ambulances were deployed, as well as more than 100 national disaster medical assistance teams, with all Halloween events being called off by authorities at 23:19.

Dealing with disaster

Videos from the scene show dozens of people attempting CPR on victims in the street. Dead bodies lay covered with blue sheets.

Ana, a 24-year-old from Spain was also in the area, with her friend, Melissa, a 19-year-old from Germany. The pair were in a bar and tried to leave at about 23:00 when they saw ambulances trying to enter the alley and police asking people to move to make way for dead bodies and the injured.

"There were so many people that they needed normal people to do CPR. So everyone started jumping in to help," Ana told the BBC.

The first confirmed death toll was issued at 02:30. Official said that 59 people had died and a further 150 were injured. An hour later the numbers had risen to 120 dead with 100 injured, and climbed further still as the night wore on, soon surpassing 150.

Within hours of the tragedy unfolding South Korea's President Yoon Suk-yeol had held an emergency meeting, and announced an investigation into the cause of the crush. On Sunday morning he announced a period of national mourning.