Police and local authorities made mistakes in the handling of two illegal raves where a man died and a woman was raped, a mayor has said.
About 6,000 revellers descended on the village of Carrington and Daisy Nook Country Park on Saturday.
Greater Manchester Mayor Andy Burnham admitted intelligence gathering on both events "could have been done better".
A 20-year-old man died of a suspected drug overdose at the Daisy Nook rave in Failsworth while a woman was raped and three people stabbed in Carrington.
Both events late on Saturday were illegal under coronavirus restrictions but Greater Manchester Police restricted its involvement to what they called "careful monitoring".
Speaking at an online news conference with Assistant Chief Constable Nick Bailey, Mr Burnham said the force was ready to take every step necessary to stop other illegal raves and that officers would not turn a blind eye in the future.
The mayor urged the public to tip off police to help them prevent and disrupt any similar gatherings.
Mr Burnham said there had been "little intelligence of a precise nature" in Carrington and GMP had arrived to find a large number of people there.
He said communication with local authorities "wasn't as good as it could have been" and promised "a stronger, more interventionist approach in future" including more officers as part of an action plan.
Addressing young people he said: "You are putting yourself at severe risk of harm".
There was "no excuse" for parents who might drop their children off to attend, he said, and anyone caught organising such events would face prosecution, he added.
The conference also heard one of the Carrington stabbing victims, an 18-year-old man, has now been released from intensive care.
- 15 June