Three people have been charged after violence erupted at a mass gathering at The Meadows in Edinburgh.
Police Scotland said "thousands" of people gathered at the park to enjoy the sunny weather on Saturday.
The force condemned "blatant anti-social behaviour" after social media footage emerged of young men fighting and throwing debris.
Officers were called to a series of incidents over the course of the day and told "hundreds" to move on.
Ch Insp Sarah Taylor said: "We are aware of the extent of the disorder seen in The Meadows this weekend and we absolutely condemn this.
"Officers were called to a number of incidents and responded quickly and professionally in the face of some blatant anti-social behaviour.
"We've been working with the council and are committed to tackling these issues together, both in the immediate future and long-term. There will be zero tolerance."
Scottish Police Federation chairman David Hamilton said one officer at the park was hospitalised with a facial injury - and that public hostility toward the restrictions was "foreseeable" and had been "growing for some time".
He added: "Countless other unvaccinated officers were put at risk, for simply doing their jobs to keep others safe."
Ch Insp Taylor said there would be a police presence in the area over Easter and the coming weekends "as a minimum".
Three people were charged in connection with anti-social behaviour and a serious assault.
Officers are working to trace others involved in various incidents and have appealed for witnesses.
In particular, they are looking to speak to anyone who saw a 22-year-old man being attacked at about 19:30 in the Middle Meadow Walk or a 17-year-old man being seriously injured in the park around 18:40.
'Doesn't feel safe'
Diane Gray, who lives in the area, said the Meadows has been very busy on sunny days with "hordes of young people congregating".
Ms Gray said there had been problems with litter, including human waste, broken glass and "drug paraphernalia".
She said: "I am older, restricted mobility, and I keep well away on days when it's busy because it doesn't feel safe."
A clean-up operation by both council employees and volunteers was praised on social media.
Officers are urging people to stay local and to follow government rules on outdoor meetings.
Ch Insp Taylor added: "I would like to thank those who are sticking to the rules and doing the right thing to avoid the spread of the virus as we move through the easing of restrictions.
"Our approach throughout the pandemic has been to engage with the public, explain the legislation and encourage compliance, but we will not hesitate to use our enforcement powers as a last resort."