Britain has expelled five Libyan diplomats to protest at the Libyan government's actions and because they could pose a threat to national security, Foreign Secretary William Hague said on Wednesday.

"To underline our grave concern at the regime's behaviour, I can announce ... that we have today taken steps to expel five diplomats at the Libyan embassy in London, including the military attache," Hague told parliament.

"The government also judged that were those individuals to remain in Britain they could pose a threat to our security," he said.

He also said a British diplomatic mission, headed by a senior diplomat, visited the eastern Libyan city of Benghazi on Monday and Tuesday to meet opposition groups, including Mustafa Abdel Jalil, head of the rebel Libyan National Council.