Pictures of large crowds gathering in Liverpool two hours before new Covid-19 restrictions came into effect “shame our city”, its mayor has said.
Footage on social media showed people dancing and surrounding a police car in Concert Square at 22:00 BST.
Liverpool City Region is the only area in the top tier of the government’s new system of restrictions.
Mayor Joe Anderson said ignoring facts about the virus was “why we are in Tier 3 measures”.
The new rules mean pubs in the city region not serving meals must stay shut, along with gyms, leisure centres, betting shops and casinos.
The crowds gathered as nearby bars closed but police said they were dispersed quickly and safely, although 38 fixed penalty notices were issued for breaching coronavirus legislation.
Merseyside Police Chief Constable Andy Cooke said he was “absolutely livid” when he saw the scenes and described those involved as “selfish, dangerous and childish”.
He said the “vast majority” of people were abiding by the rules but those who were “blatantly disregarding the law” were putting extra pressure on the force.
Liverpool currently has the third highest rate of infections in England with 635 cases per 100,000 of population up until 10 October, behind Nottingham which has 880 and Knowsley with 667.5.
Paul Brant, cabinet member for adult health and social care, said intensive care beds in the city were at more than 90% capacity and were soon expected to reach or exceed the levels of occupancy seen during the first wave.
He added: “At the current rate of increase, we would expect Liverpool to surpass the peak of the first wave probably within the next seven to 10 days.”
Mr Anderson, reacting to footage circulating of the crowds on social media, tweeted: “These pictures shame our city.”
He added: “Our health service is creaking, 300 in hospital & 30 people dead in [a] week. Ignoring these facts is why we are in Tier 3 measures.”
Mr Anderson, who previously called for a circuit-breaker lockdown, questioned whether the measures would be enough to tackle the “uncontrollable” spread of the virus and called for unity.
“This city is in a Covid crisis. It’s an enemy we are really finding it hard to get on top of and defeat,” he said.
“We need to keep working together and pulling together.”
City councillor Nick Small said those involved were “idiots putting themselves, their friends, families and everyone else at risk, destroying jobs and our hospitality sector while they do it”.
Calum Semple, professor of outbreak medicine at the University of Liverpool and a member of the Scientific Advisory Group for Emergencies, said hospitals in the city faced a “dire situation”.
He appeared in a video message issued by the city council and urged the public to “please pay great attention to the regulations that are being brought in”.
Prof Semple said: “We have got over 300 patients in beds and our intensive care capacity is currently running at 90%.
“At this rate we are looking at exceeding healthcare capacity in the next week or so.”
Richard Kemp, leader of the city’s Liberal Democrat group, warned against scapegoating Liverpool’s young people for something involving “at most 300” people.
“What they did was wrong and they should be ashamed of their behaviour,” he said.
“However, we have 60,000 students in our city and a very large number of our resident population under 25.
“This means that 99.99% of the city’s young people behaved themselves last night and should be congratulated for their restraint.”
Liverpool musician Ian McNabb took to social media to support youngsters “partying loud and hard on the last night before the shutdown”.
“If I was 18 I’d be right there with them,” the former frontman of the Icicle Works posted on his Facebook page.
Ch Supt Peter Costello, of Merseyside Police, said: “While we understand the new rules are frustrating for some, we would continue to advise everyone to abide by them – including keeping social distancing – for the safety of everyone.”
Chris Ellerby-Hemmings, co-owner of EmpoweredFit gym in the Wirral, said: “We are not staying open for financial gain but more for our members’ mental and physical well-being.”
One gym owner who has closed his business said it was a “huge blow not just for myself but for the people in the local community who come here”.
Mick Povall, owner of Gravity Health and Fitness in Upton, Wirral, said: “The government carries on about the importance of improving mental health and avoiding obesity during the pandemic and then in the same breath shuts down one of the best tools to achieve those goals.
“If we don’t reopen soon, we might never reopen.”