LONDON -- Libyan Foreign Minister Moussa Koussa arrived in the U.K. on Wednesday and is resigning from his post, Britain's government said.
Moussa arrived from Tunisia at Farnborough Airport, about 35 miles southwest of London, the Foreign Office said in a statement, adding that he traveled here under his own free will.
"He has told us that he is resigning his post," the statement said.
"We are discussing this with him and we will release further details in due course."
Moussa Ibrahim, a Libyan government spokesman, denied that the foreign minister has defected saying he was in London on a "diplomatic mission."
"He is on a diplomatic mission. He has not defected," Ibrahim told reporters in the Libyan capital, Tripoli.
It was not immediately possible to confirm either statement with Moussa or people close to him.
"We encourage those around Gadhafi to abandon him and embrace a better future for Libya that allows political transition and real reform that meets the aspirations of the Libyan people," the Foreign Office statement said, indicating that discussions with Moussa would be ongoing.
Guma El-Gamaty, an organizer in Britain for a leading Libyan opposition group, said Moussa's action would be "a big hit" that would weaken Gadhafi.
"He says he is resigning, that means he is defecting," he said. "That means he is defecting. He has been Gadhafi's right-hand man for years, running intelligence, running the Lockerbie bomber negotiations, running many things."
El-Gamaty said he does not think Moussa is likely to remain in Britain but would likely end up in another country in an effort to avoid possible prosecution.
Moussa's unannounced arrival in Britain followed hours of unconfirmed reports about his travel plans. Tunisia's official news agency had reported that he had arrived in Tunisia Monday for a "private" visit, without elaborating.
A Tunisian diplomatic official, who spoke on condition of anonymity, told the Associated Press that Moussa had met a "foreign delegation" at his hotel in Djerba.
The agency's report Wednesday said he had been accompanied by Libya's vice-minister for European affairs, Abdelati Laabidi, who returned to Libya.
Moussa was reported to be carrying a diplomatic passport.