Libyan Foreign Minister Moussa Koussa has been questioned by officials after arriving in the UK unexpectedly on Wednesday.

He flew in from Tunisia. The UK Foreign Office said he was "no longer willing" to work for Colonel Gaddafi.

However a Libyan spokesman denied that Mr Moussa had defected and said he was on a diplomatic mission.

His arrival in the UK comes as Libyan rebels retreat from former strongholds along the eastern coast.

They are in full retreat from Brega, having lost the key oil port of Ras Lanuf and the nearby town of Bin Jawad.

In the west, the rebel-held town of Misrata is still reportedly coming under attack from pro-Gaddafi troops, reports say.

'Own free will'

A British Foreign Office spokesperson said Mr Koussa - who is in his early 60s - had arrived at Farnborough airport, west of London, on Wednesday evening.

"He has told us that he is resigning his post. We are discussing this with him and we will release further details in due course.

"Moussa Koussa is one of the most senior figures in Gaddafi's government and his role was to represent the regime internationally - something that he is no longer willing to do.