Police say they were 'met with hostility' when they tried to break up a rave in the city centre.
A large crowd of people gathered in the sunshine at Castlefield Bowl on Wednesday.
Footage from the scene showed scores of people singing and dancing as a sound system played.
Police say officers were monitoring the situation throughout the day.
And the numbers present began to increase in the early evening officers 'attempted to engage with a group at the scene but they were met with hostility causing them to withdraw'.
Extra police were drafted in and the rave was eventually dispersed peacefully.
No fines have been issued but an investigation is underway and police are attempting to track down the organiser.
Two 18-year-old men were arrested on suspicion of indecent exposure, but later de-arrested.
Insp Jonathan Shilvock of GMP City of Manchester division, said the rave was a 'clear breach of the coronavirus rules and regulations'.
He added: "As a result of this gathering we were forced to deploy additional officers from across the City of Manchester division.
"Thankfully, upon their arrival the group did quickly disperse at the sight of them; however this was a clear breach of the coronavirus rules and regulations.
"We appreciate that people will want to socialise due to the warm weather and the recent relaxation of the rules, but I want to remind people that this pandemic is not over and we all share a collective responsibility in complying with the rules and keeping infection rates down.
"Restrictions remain in place; outdoor gatherings (including in private gardens) can take place, but of either six people (from separate households) or two different households (linked households are counted as one).
"I would like to thank all those who have played their part and been compliant with the rules as you are playing a vital role in slowing the spread of the virus.
"We will however continue to issue fines to those who ignore and show complete disregard to the rules."
