Police were today liaising with university staff after 20 students were arrested in a violent anti-war protest.

The demo at the University of Sussex campus in Falmer began when students and members of pressure group Brighton Against The War occupied the offices of the university's Royal Navy unit on the fifth floor of an arts block.

About 20 people barricaded themselves into the office, saying they wanted to register their anger at the American and British bombing of Afghanistan.

A navy officer was barricaded inside as more than 200 students gathered outside the building with the intention of storming it.

One student said: "There is not much we can do about the war in terms of stopping it but we want to register our resistance to it and our refusal that it should be carried out in our names."

Police were called to the scene to negotiate with the occupiers, who were eventually persuaded to leave the building almost three hours later on Friday. One officer was hurt in the melee.

Police arrested 20 people on suspicion of false imprisonment and criminal damage. They were questioned and released on police bail.

Chief Inspector Kul Verma said: "People are entitled to protest so long as they do so peacefully and lawfully.

"The action was not lawful and the police response has been robust and appropriate."

A police spokesman said: "It was quite unusual circumstances with this chap being imprisoned in his own office.

"It has caused a certain amount of upset at the university. We will be co-operating with them to see what measures need to be taken."