Police arrested 21 people as violence marred the end of an unofficial street party in Glasgow's Kelvingrove Park.

Thousands of people poured into the park on Friday in response to an invitation on Facebook, in defiance of warnings by the city council to stay away from the event.

Initially the festivities were good-natured, with between 3000 and 5000 people drinking and dancing in the sunshine to sound systems laid on by the organisers.

But by 5pm scuffles had broken out between police and revellers, with bottles and cans thrown at officers and two police vans having their windows smashed.

Police on horseback responded by charging the remains of the crowd on horseback as the gathering began to break up.

Organisers arranged Friday's event through the social media website, prompted by a statement by Prime Minister David Cameron that people should have a street party on the day of the royal wedding if they wanted.

Police patrolled the park and initially appeared to be taking a low-key approach to the festivities.

A handful of union flags were in evidence, but the event was not explicitly linked to the wedding of the Duke and Duchess of Cambridge, which took place in Westminster Abbey, London, several hours earlier.

Glasgow City Council had earlier advised people not to attend the party in Kelvingrove Park because of health and safety concerns.

The council says organisers of legitimate events must have permission to use it. They must also satisfy the council that they will take safety precautions such as providing first-aiders, sufficient public toilets and stewards, as well as obtaining public liability insurance.

The organisers claimed they had a "go ahead" and public liability insurance.

They added: "We have sound equipment, DJs, an afterparty organised. Bring your mates, some food, and make a day of it."

A council spokeswoman said: "We advised people not to attend this unplanned and unauthorised party."

The event was organised after David Cameron attacked "pen pushers and busybodies" for thwarting royal wedding celebrations on health and safety grounds.

Speaking at an event in Harrogate in Yorkshire, on April 11, he said: "They have no right to stop you from having fun. I am the Prime Minister and I am telling you if you want to have a street party, you go ahead and have one."

Only a handful of officially organised street parties have been held in Scotland to mark the royal wedding, the majority of which were in Edinburgh.