Four people have been arrested after protesters sprayed fake blood and occupied offices in a building where an international arms fair is being organised, police have said.

Protesters objecting to the Defence Systems Equipment International exhibition gathered outside the offices of Spearhead, the exhibition organisers, in New Malden High Street, southwest London, about 8am today.

Some of the protesters sprayed fake blood and three women, apparently dressed as office workers, then went inside the building and barricaded themselves in an office.

They were later removed after office staff took out a glass panel.

The three were arrested on suspicion of criminal damage and theft.

Another person was arrested outside the Spearhead offices, on suspicion of minor criminal damage, and all four suspects were taken to south London police station.

A statement from protesters said about 15 people took part, although police said there were eight participants.

One of the protesters, Sally Mander, said the organising of the exhibition was a crime against peace.

“This arms fair is a hideous market place of weapons of mass destruction and we’re not prepared to stay at home and ignore the trade in death that’s going on right under our noses,” she said.

The Defence Systems Equipment International is due to be held at ExCel next month.

A Spearhead spokesperson said the company worked very closely with the Ministry of Defence on the exhibition.

Protesters did not seem to like the fact that the UK had a strong defence industry, the spokesperson said.