A series of giant Olympic rings have been launched on the River Thames, to mark the fact that there are 150 days to go for the start of the 2012 London Olympic Games.

The rings are 11m high and 25m wide and coloured with the traditional red, yellow, green, black and blue of the Olympics insignia on one side and have Light Emitting Diodes (LED) on the other.

The rings started their journey down the river at London Bridge and will move on to Canary Wharf and Tower Bridge before going into storage.

"London and the UK's creative industries are world-beating and the London 2012 Festival will show them off to the world. With millions of free tickets and opportunities to take part, Londoners and tourists will truly have a summer like no other, thanks to the partnership between the mayor's office and London 2012 Festival," Ruth Mackenzie, director of the London 2012 Festival was quoted as saying by the BBC.

Meanwhile, the Mayor of London, Boris Johnson, announced cultural events for the London 2012 Olympics. These include floating operas, pop concerts and interactive public artwork by Jeremy Deller and London Pleasure Gardens.