Leeds City Council claims about 350 people armed with water pistols and buckets trashed the city's Millennium Square garden.

The square's stunning centrepiece, which scooped a bronze medal at the 2004 Chelsea Flower Show, is a symbol of the city's enduring partnership with Nelson Mandela and his hometown of Durban.

But council chiefs claim years of work establishing the garden's exotic greenery were ruined when about 350 people took part in the water fight on Monday.

Videos and pictures of people trashing the garden have been posted on the social networking website and footage also features on the YouTube video website.

Organisers even boast of the "success" of their "event", the council said.

Plants were trampled, turf ripped up, water features emptied and filled with foam and the mechanism for the fountains is thought to have been damaged during the Bank Holiday rampage.

Council CCTV footage will now be handed over to the police.

Councillor John Procter, executive member for Leisure, said: "Our parks staff were distraught when they discovered the wreckage.

"Frankly I'm appalled at the total disregard for people's ongoing enjoyment of this beautiful city centre oasis."