Anti-war protesters of all ages took to the streets of Sussex today, hours after the first US cruise missiles hit Baghdad.

Hundreds of people, many of them schoolchildren, brought traffic to a standstill as they marched through central Brighton.

Police appeared at times to lose control as a rally from the Old Steine broke away towards Castle Square en route to Churchill Square shopping centre.

Long lines of buses and cars backed up in North Street and Western Road, gridlocking the entire area as some demonstrators began to sit down, blocking roads.

The protest was the first of a number of demonstrations planned for today, organised by Sussex Action for Peace and students from Brighton University.

Placards and banners encouraged drivers to "honk for peace" and many did, although there were occasional retorts of "Get back to school" from frustrated motorists.

Others banners read: "Blair: the real terrorist" and "stop the city".

At least four police patrol vans and around 50 officers were on hand to marshal the crowds.

The officers had been briefed to allow the protesters to express themselves while also keeping traffic moving. There were no reports of arrests.

Student Ben Hudson, 21, said: "We need to keep the campaign going to show solidarity with the people of Iraq and to continue to put pressure on the Government."

A group of pupils from Varndean School chanted: "Who let the bombs out? Bush and Blair."

Nick Dunford, 50, from Brighton said: "We live in a country in which lies have become the truth and the truth has become lies."

By lunchtime 500 demonstrators who gathered outside Churchill Square began making their way down West Street along the seafront to Brighton Town Hall.

They intended to remain in the city centre until 5.30pm, when they expected their ranks to be swollen by returning workers at a high-profile rally.

Superintendent Peter Coll, second-in-command of Brighton and Hove police, said: "We want to facilitate peaceful protests and people's right to protest but any threat of violence or damage to property will not be tolerated and we will take a firm line."

About 300 children stopped traffic by staging an anti-war march in Haywards Heath today.

They waved banners and chanted slogans as they took over pavements and walked on roads.

The group headed through the centre of town and into the Orchards shopping centre, then left via South Road.

One shopper said: "There were between 200 and 300 children. The police were trying to move them on but there were too many of them."

Other demonstrations planned for today included:

-At 4pm a rally organised by Unison, the public sector workers' union, was expected to be held at St Bartholomew's Square outside Brighton Town Hall.

-At 5.30pm a main demonstration was planned to take place at Churchill Square, Brighton.

-Churches across Eastbourne planned to toll their bells at precisely 6pm. People were set to gather inside Our Lady of Ransom Church by the town hall in Grove Road.

- In Mid Sussex protests were taking place in Burgess Hill and Haywards Heath as part of a national demo at 5.30pm.

City centre buildings in Brighton were daubed with anti-war slogans early today.

A man aged 24 was arrested at 1am on suspicion of 11 separate offences of criminal damage. He was helping with inquiries.

Buildings in Dyke Road and round the Clock Tower were daubed with spray paint.

Reporting by James Lancaster and Phil Mills