Hundreds of people attending large gatherings including raves and street parties have been dispersed by police.
West Midlands Police officers discovered more than 300 people at an illegal rave in Birmingham city centre on Saturday.
It was one of 80 gatherings the force said it had had to deal with over the weekend.
Chief Constable Dave Thompson said there was "no place for these in a pandemic".
Across the city, the force recorded about 200 people "crammed into a communal area with sound systems" at a block party.
People at the events were "flaunting regulations and causing significant disruption to the communities around them", Supt Jack Hadley said.
"Such selfish behaviours will not be tolerated."
He said the parties were "dangerous", adding that detectives were "gathering evidence to allow us to prosecute the organiser".
The parties come as the weekly rate of coronavirus infections in Birmingham more than doubled, rising from 13.8 per 100,000 people to 28.1, with 321 new cases.
Birmingham City Council has urged "continued vigilance", saying the city "can't afford to drop our guard".
Last weekend, the force broke up 28 separate large gatherings and street parties, including one music event in Nechells attended more than 70 people.