By Tim Weber
Business editor, BBC News website, DSEi in London
Protesters have been arrested as they tried to invade one of the world's largest defence fairs in London.
Protesters have vowed to disrupt the DSEI event
Arms trade critics, shouting "murderers" at exhibitors, were quickly overwhelmed by police after breaking through the initial security cordon.
The Metropolitan Police say between 15 and 20 people were arrested for a suspected breach of the peace.
Further disruption is expected later when pressure group Campaign Against Arms Trade holds a demonstration.
Held every two years, the Defence Systems & Equipment International show attracts more than 1,350 exhibitors and military delegations from 56 countries.
The DSEI event is a showcase for weapons systems, ranging from logistics software to tanks and rocket launchers.
Soldiers and exhibitors come not just from the UK, Germany, the US and other Nato countries, but from countries such as Libya, Russia, Saudi Arabia, Iraq, Pakistan and India.
However, as in previous years, the organisers have ordered exhibitors not to show any equipment that might be considered too offensive - such as torture devices and cluster bombs - neither as an exhibit, nor in pictures or literature.
As well as the Campaign against Arms Trade protest, other campaigners have threatened to try to disrupt the event using "direct action".
Public pressure has persuaded the company organising the show, Reed Elsevier, to sell the business by the end of the year.
Security around the London venue is tight
DSEI spokesman Al Lockwood said the sale was on track and that bids for the show were currently being assessed.
He added DSEI had a "bright future" and would be held again in September 2009 at the same venue.
"We are well aware that DSEI has its critics," Mr Lockwood said, adding that organisers had designated an area where demonstrators could protest and would be visible to visitors arriving at the exhibition.
There had been doubts about the future of the exhibition, after Prime Minister Gordon Brown decided to abolish the government's Defence Export Services Organisation (DESO), which helps to organise the show and hosts all foreign military organisations.
In another snub to the industry, the UK's defence secretary has broken with tradition and will not open this year's event.
However, the promotion of arms exports as such has not ended, with DESO's function to be moved to UK Trade and Investment department by the end of the year.