Four people were arrested outside RAF Brize Norton during a demonstration over claims that US planes carrying arms are stopping to refuel at the base on their way to Israel.

Police said two men and two women, three from South Wales and one from South London, were arrested on Saturday as about 40 protesters gathered outside the base.

One woman from Cardiff was charged with assaulting a police officer and released on bail.

The other three were cautioned for obstructing a highway.

A police spokesman said there were 10 Thames Valley and Ministry of Defence police officers outside the base throughout the day and the demonstration was otherwise peaceful.

Peace campaigner Sarah Lasenby, 68, from Oxford, said the individuals involved were connected to the Cardiff Anarchist Network.

She said the group entered the base's main entrance with a banner and were arrested after running out into the road, causing problems for motorists.

Ms Lasenby - who was among seven campaigners arrested last Monday at Prestwick Airport, in Scotland, and charged with entering a restricted zone - said: "It rather spoilt the demonstration, which I felt had been effective up until that point.

"The police were sensible - for once - and didn't have much choice but to move in when they did.

"It's a shame, because the whole point is that we want to get the message across that we shouldn't be allowing US aircraft to fly into Britain. In my view, it's a war crime."

Members of Oxford and Swindon Stop the War Coalitions staged the demonstration.

A peace camp was set up in the grounds of Alvescot Church yesterday.Sun Ms Lasenby said campaigners planned to monitor aircraft flying in and out of the base.