Met police say one officer stabbed along with two members of the public, while another officer injured by a bottle

Police in riot gear were deployed in Hyde Park in central London on Tuesday after an event originally described as a free party and water fight turned ugly – with one officer stabbed and another injured after being hit with a bottle.

The violence started earlier in the afternoon when a crowd of young people began gathering in the park on what was the hottest day of the year so far. According to witnesses posting comments on social media, a largely good-natured crowd were told to disperse by police officers, prompting some to start throwing bottles.

Later in the evening two members of the public were taken to hospital suffering from stab wounds. The two police officers were also treated in hospital and subsequently discharged.

Images posted on social media show scores of young people gathering as police officers, many carrying riot shields, tried to clear the area. The crowds did not disperse until 2.20am on Wednesday, police said.

One video on Twitter, posted by an account called ‘YT_Bricks’, showed parts of the disturbances and can be heard saying “... they are throwing bottles at Fed cars ... they are mashing up the Fed cars.”

Earlier this week, flyers had been distributed on social media advertising a free party, which brought hundreds of young people into the area. The unofficial event follows large parts of the park being closed to the public last week as the royal parks hosted their British Summer Time concerts, featuring stars such as Stevie Wonder, Pharrell, Carole King and Massive Attack.

There had been anger expressed by residents living nearby at the noise of the gigs, and by community activists at the fact what was once a public open space was now being used to make promoters and the royal parks large sums of money while blocking off access to local communities.

At 10pm, the Metropolitan police said they were still dealing with “disorder”. A police spokesperson confirmed two officers suffered injuries – one stabbed and another hit with as bottle – and that two others were also reported to have been stabbed and had been taken to hospital.

A statement added: “Police in Westminster were in attendance at Hyde Park, by the Serpentine, from 3pm after a large number of people gathered for a spontaneous ‘water fight’.

“At around 8.40pm, parts of the increasingly large crowd become hostile to police and items – including bottles – were thrown towards officers.”

Westminster Conservative councillor Glenys Roberts, said many residents in areas around Hyde Park felt increasingly disenfranchised by the use of the park during the summer for commercial events, and that free parties could be a response to them.

She added: “The concerts are a great nuisance. Many feel strongly that the park is a free space that should be open to everybody. The concerts do not even seem to make enough money to repair damage to the grass or improve the park for the enjoyment of all.”

A spokesperson for The Royal Parks said “Event organisers pay for reinstatement of the park after events. The Royal Parks holds concerts to bring in the much needed self-generated funding to keep the parks in the amazing state that millions of people enjoy every year. Over the past 10 years we’ve seen our government grant reduce by about 50% so these funds are vital to the upkeep of Hyde Park.

“Just 11 per cent of Hyde Park is taken up for the concerts and during that two-week period that area is open more than it’s closed with a range of free activities taking place during the week. We have worked hard with our event partners to minimise any disruption and this approach has meant that complaints have reduced year on year. And 2016 was no exception.”

• This article was amended on 22 July 2016 to append a quote from The Royal Parks.