Manchester police said the events - attended by up to 4,000 people - had "tragic consequences" with one death, three stabbings and an allegation of rape.
One person died and at least three people were stabbed at illegal raves in Manchester on Saturday, one of which was attended by at least 4,000 people, according to police.
Manchester police also announced an investigation after an accusation of rape made by an 18-year-old woman.
Assistant Chief Constable Chris Sykes said the raves - organised despite restrictions put in place to stop the spread of coronavirus in the UK - “have had tragic consequences”.
The UK has one of the highest death rates for coronavirus in the world, and the north-west has one of the highest rates of infection in the UK.
Police said around 4,000 were at the rave in Droylsden, where a 20-year-old man died from a suspected drug overdose.
Carrington, where there were around 2,000 at the peak, saw three separate reported stabbings, with one 18-year-old man left with life-threatening injuries.
Police officers were also attacked by some of the attendees.
Illegal raves in Berlin
It wasn’t just the UK that saw illegal gatherings and attacks on police this weekend.
There were 15 arrests, and 34 criminal investigations opened after two separate gatherings in parks in Berlin, Germany on Saturday.
Police said 400 people attended one gathering, and 500 another, where police and emergency services were pelted with bottles and assaulted by the attendees.