China's President Xi Jinping has demanded an investigation into Shanghai's New Year's Eve crush that killed 36 people and injured 47.
The crush happened in Chenyi Square in the Bund district, where huge crowds had gathered for the countdown.
The turnout was much higher than predicted, and Shanghai police said they regretted their failure to intervene in time, state media said.
Police are investigating what sparked the crush.
The government cancelled New Year's Day festivities in Shanghai.
Xi Jinping told Shanghai officials to provide an explanation for Wednesday's fatalities as soon as possible, and to "go all out" in efforts to treat the injured, state media reported.
Mr Xi added that local officials around China should ensure that no repeat of the Shanghai incident could occur elsewhere during the upcoming Lunar New Year festival.
The crush began at about 23:35 local time (15:35 GMT) on Wednesday.
Investigations are expected to examine how Shanghai police managed the new year crowds.
Official New Year celebrations had already been cancelled at the Bund due to fears of overcrowding, state-run news agency Xinhua said, citing local officials.
However, despite the cancellation, there were "far more" people in the area on Wednesday evening than predicted, with a crowd size similar to the countdown in 2013, it added.
Close to 300,000 people reportedly turned up for New Year's Eve celebrations in the area a year ago.
Shanghai police said that about 700 police officers were located in the area, and 500 were deployed after overcrowding was seen near Chenyi Square, Xinhua reported.
The police expressed regret that they had not managed to "effectively intervene" when the flow of tourists in the area "increased irregularly" at 23:30 (15:30 GMT), the news agency added.
Cai Lixin, a deputy police commander, said in quotes carried by Chinese media that there had been fewer police deployed than for some other events.
"There were no formal events planned yesterday, so we did not arrange for as many police officers as last year's national day," he said.
The crush centred on a stairway leading to a viewing platform near the waterfront, as people tried to get up and down the steps, state broadcaster CCTV said.
A local resident, identified as Sarah, told AFP news agency "people were screaming... and people [started] jumping off the staircase to get clear."
She added: "There was a quiet, and then people on the stairs fell in a wave."
Mourners light candles in the shape of a heart at a makeshift memorial at the site of a stampede on the Bund in Shanghai, China, 1 January 2015
A memorial has been set up on the Bund
Gaby Gabriel, an American photographer living in Shanghai, told the BBC: "It was a tremendous amount of people moving in all different directions.
"It seemed some people were trying to move away from the river and some people were trying to go towards the river and there was no order whatsoever, no guidance."
However, Shanghai police denied social media reports that a stampede was triggered by people stopping to pick up fake money thrown from the balcony of a nightclub.
In a statement, police said that video footage showed that the bills had been thrown after the crush took place.
Shanghai's city government said that the identification process for victims of the crush had begun.
A Taiwanese person was among the dead, and there were two Taiwanese and one Malaysian among the injured, it added.
Angry family members clash with security personnel in a hospital where some of the victims of a stampede by new year's revellers were sent in Shanghai, 1 January 2015
Earlier, some relatives jostled with police as they waited for news of their loved ones in hospital
A Malaysian student in China also died in the crush, Malaysia's foreign ministry said.
Many of the dead are believed to be students, state media report.
Some relatives have criticised the authorities, saying they were not kept informed, AP news agency said.
"We were told my sister was still being rescued the minute before we were taken to the morgue, where she had been lying dead, clearly for a while,'' Cai Jinjin, whose cousin Qi Xiaoyan was among the dead, told the agency.
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