Thousands of anti-war protesters joined peace rallies in London and across the UK on Saturday.

An estimated 100,000 people packed the streets of the capital on a march to Hyde Park to protest against the war on Iraq.

Campaigners were hoping as many as half a million people would join the rally, but recognised the hastily arranged event was unlikely to be on the same scale as February's huge demonstration in the capital when more than a million people came together to urge Prime Minister Tony Blair not to commit British troops to the military conflict.

Organisers, however, believed it could still be the biggest ever demonstration in this country during a war.

The biggest event on Saturday was being held in London, where left wing Labour MPs were joining union leaders and schoolchildren in addressing a huge rally in Hyde Park.

The Stop The War Coalition (STWC) said it was expecting a "substantial demonstration" against the UK's involvement in the war on Iraq.

Coach-loads of demonstrators travelled to London from across the country to take part in the march and rally.

Speakers will include Labour MPs Alice Mahon, Jeremy Corbyn and George Galloway, and union leaders Bob Crow (Rail Maritime and Transport union), Keith Sonnet (Unison) and Billy Hayes (Communication Workers Union).

Elsewhere in the UK, opponents of the war in Scotland joined peace marches in Glasgow, Edinburgh, Inverness, Dundee and Aberdeen.

Around 100 protesters turned out in Tony Blair's Sedgefield constituency in the North East, while the US base at Menwith Hill in Yorkshire and RAF Fairford in Gloucestershire were also picketed.

The UK demonstrations were part of a co-ordinated day of anti-war rallies around the world.

Tens of thousands of people joined peace marches in Australia, New Zealand, Japan, France, Italy and Greece, while anti-American demonstrations were held in several countries, including India, Yemen, Indonesia, Malaysia and Bangladesh.