Anti-war protesters last night said they would continue to do all they could to stop American military chiefs from stockpiling cluster bombs after they were sentenced for breaking into a Suffolk airbase.

Anti-war protesters last night said they would continue to do all they could to stop American military chiefs from stockpiling cluster bombs after they were sentenced for breaking into a Suffolk airbase.

Seven campaigners walked from court with conditional discharges after being found guilty of criminal damage and trespassing at RAF Lakenheath after they cut through a fence and chained themselves to the base's munitions compound during a protest against the use of the controversial explosives.

During the four-day trial at Ipswich Crown Court, US Air Force officials admitted for the first time that cluster munitions were stored at the Suffolk military base.

Five women and two men were yesterday given conditional discharges for 12 months and ordered to pay £250 each in costs following their actions at RAF Lakenheath on October 2, 2006.

Mell Harrison, 37, of Dunburgh Road, Geldeston, near Beccles, Peter Lux, 46, of Hughenden Road, Norwich, Lesley Graham, 49, of Hardy Road, Norwich, Richie Rushmere, 40, of Norwich, Irene Willis, 63, from Essex, Lesley Anderson, 26, of Scotland, and Emma Bateman, 41, of Leicester, all denied trespassing on a protected site and claimed their actions were lawful because they had stopped USAF F-15E jets from dropping cluster bombs in Iraq.

Margaret Moss, 55, of Norwich, was also arrested as a member of the “Lakenheath 8”, but died last year after losing her fight with cancer.

After yesterday's hearing, the anti-war campaigners submitted letters to the Crown Prosecution Service (CPS) and Ministry of Defence Police calling for them to investigate the USAF for its “war crimes” in Iraq and Afghanistan.

Mell Harrison, eastern region campaigns officer for the Campaign for Nuclear Disarmament (CND), said she would continue the fight until the US signed the Convention on Cluster Munitions treaty and disposed of all cluster bombs from the Suffolk base.

“We will continue to campaign in every way we can to stop the killing of innocent men, women and children. The US needs to remove these cluster bombs from our country. They are committing war crimes that the UK government cannot do anything about,” she said.

Ipswich Crown Court heard that the eight protesters cut through the perimeter fence at RAF Lakenheath in the early hours of October 2 and spent about three hours chained to the fence of the weapons compound.

The protesters argued that all other methods of bringing the issue to the attention of the authorities had proved fruitless. But the prosecution said the possession of cluster bombs was not a crime and the defendants did not have the right to take the actions they did.

After the hearing, David Hutson, senior crown prosecutor, said it was a “very complicated and unprecedented case” and was only the second time that the CPS in England and Wales had prosecuted for the offence of “Trespassing on a site designated by order by the Secretary of State”.

No one from RAF Lakenheath was available for comment last night.

But Cdr Bob Mehal, US Department of Defence spokesman, said the US military had recently begun a 10-year policy of replacing its least reliable cluster bombs. He added that the US had provided more than $1.4bn since 1993 to aid the clean-up of landmines and “explosive remnants of war”.

“Cluster munitions are legitimate weapons that provide a vital military capability when used properly and in accordance with existing international humanitarian law. Use of cluster munitions can result in less collateral damage to civilians and civilian infrastructure than unitary weapons,” he said.