But visitors could still reach the Royal Navy and British Army Equipment Exhibition (RN&BAEE) through alternative entrances. One protester broke into the main concourse, where he climbed on to an exhibition stand. Police were unable to bring him down as he harangued delegates and exhibitors for an hour.
The Campaign Against Arms Trade (CAAT), which said 1,000 people were involved in the protest, accused the Government of failing to keep to an ethical foreign policy. Rachel Harford, joint co-ordinator, said she had not expected such a good turn-out.
"There is a lot of concern about a government that is saying one thing and doing another. They should not be hosting an arms fair like this at which there are delegations from well-documented human-rights-abusing countries such as China, Turkey and Saudi Arabia. Having an arms fair like this is giving a green light to those oppressive regimes."
She urged Tony Blair to stick to election pledges on not issuing arms licences to rights-abusing countries.
Representatives from the Kurdish community gave their full backing to the campaign and dozens joined the protest.
Protesters said the Government invited a number of countries to the exhibition that had poor records on human rights, including Turkey, Indonesia, China and Saudi Arabia.
Francesca D'Silva of CAAT said: "In allowing such delegations, the Government is breaking its election promises."
A Ministry of Defence spokesman insisted, however, that the junior defence minister John Spellar had answered the criticism of anti-arms sales campaigners in a parliamentary answer earlier this year.
Mr Spellar stated: "It is well understood by all those who attend the RN&BAEE [exhibition] that the Government considers licence applications for defence exports on a case-by-case basis.
"Attendance at the exhibition does not imply that we will licence the exports of any equipment to any particular country."
Hampshire police said 50 demonstrators were arrested for unlawfully obstructing a highway, but stressed that the protest was peaceful. One gate had been blocked but visitors could come and go freely. Police could not confirm whether any protesters had managed to climb into the airfield and said that 100 officers were policing the demonstration.
Ms Harford claimed about 40 protesters had been arrested and said six had managed to climb into the airfield, aiming to chain themselves to exhibits.
The Secretary of State for Defence, George Robertson, cancelled his visit to the exhibition following the death of Diana, Princess of Wales. Defence Procurement Minister Lord Gilbert was due to represent the Government in his place.
Later a spokeswoman for the Ministry of Defence said: "This is not a glorified arms hypermarket.
"It is a sober display of world-class defence equipment made by the best of British industry and it will be provided with pride to those who need it and who want to use it for designed defence purposes."Reuse content