Three people including a police officer have been stabbed in Hyde Park after an afternoon water fight descended into an evening of bloody violence.
Scotland Yard said one officer was knifed and another was struck with a bottle as missiles were launched at police shortly before 9pm. Both officers have been taken to hospital with injuries described as not life threatening.
Two others were stabbed in the shocking chaos which was described as a "war zone" and "riot" by stunned bystanders. The victims have also been taken to hospital but their conditions are unknown at this stage.
It comes as hundreds of youths gathered in the iconic London park on the hottest day of the year so far in the capital as temperatures soared above 32C.
Pictures from the scene show riot police have been deployed at the park amid claims it has been "shut down".
Scotland Yard said no arrests have been made so far.
Witnesses described how a “riot” had broken out in the park as a sea of police moved onto the grounds near the Serpentine where large groups had gathered for a spontaneous water fight.
Police had been stationed in the park from 3pm, Scotland Yard confirmed.
Trouble reportedly flared when police told some of the crowd to turn off their music.
A Met spokesman said: “At around 8:40pm parts of the increasingly large crowd become hostile to police and items - including bottles - were thrown towards officers.
“One male police officer suffered a head injury and has been taken to a central London hospital for treatment. An update on his condition awaits.
“Officers remain at scene and continue to deal with the incident.”
While some described the chaos as "legendary" others condemned the violence.
One woman wrote: "Good evening to everyone except those who were involved in the motiveless, opportunistic disruptions in Hyde Park today.
While Timi Marcel tweeted: "Hyde Park is a bit of a war zone."
Roads around Hyde Park including Marble Arch, Park Lane and Hyde Park Corner have been shut as a result of the disturbance.
There were also reports of an incident at a Tesco in Old Kent Road. Witnesses said the shop was ransacked by a large number of youths.
Police confirmed they were called to an incident but could not provide any further details.
Scotland Yard has asked for any witnesses or anyone with information about Hyde Park to call police on 101 or Crimestoppers, anonymously, on 0800 555 111
