"We feel very sad and extremely guilty," Vice Mayor Zhou Bo told a nationally televised press conference.
"We offer our deepest condolences to the victims, and express our deepest apologies to their families as well as the injured and their families."
An investigating team said the stampede happened at 11:35 p.m
. local time when huge crowds trying to reach the iconic riverfront promenade, known as the Bund, clashed with others attempting to leave on a staircase.
Most of the victims were in their 20s with the youngest being only 12 years old. Of the injured, three remained in a serious condition in hospital as of Wednesday.
Investigators blamed various government agencies of the city's Huangpu district, whose jurisdiction includes the Bund, for the fatal incident.
They said local officials were "ill-prepared" for the crowds and "mishandled" the aftermath.
Crowd size underestimated
Although the district authorities had earlier called off a popular riverfront light show on New Year's Eve, thousands of revelers -- unaware of the cancellation due to the lack of official updates -- still flocked to the Bund, investigators said.
They singled out the district police department for severely underestimating the crowd size -- which had reached 310,000 people by midnight -- and assigning fewer than 600 officers and other security personnel to the area.
Three top district officials in Huangpu have been sacked -- the local Communist Party boss, his deputy and the district police chief, and a total of 11 officials face punishment for their role in the incident.
In a nod to public criticism, the ruling Communist Party's disciplinary arm in Shanghai also confirmed on Wednesday that several Huangpu district officials -- including the fired Communist boss and his deputy -- violated Party regulations by wining and dining for free at a high-end Japanese restaurant on the Bund shortly before the stampede.
After Chinese President Xi Jinping warned officials about public safety following the stampede, authorities across the country have rushed to cancel large gatherings, ranging from pop concerts to shopping festivals.
But Zhou, Shanghai's vice mayor, said that, after careful risk assessments, officials have green-lighted most planned events in the city for the upcoming Chinese New Year celebrations in February -- though the popular lantern festival at the ancient City Temple won't go ahead.