An appeal court in Thailand today ruled to extradite a suspected Russian arms smuggler, Viktor Bout, to the US, effectively ending a more than decade-long chase for the man dubbed "the merchant of death".

The decision overturns a lower court's rejection of the US extradition request. The court said Bout must be extradited within three months or would be free to return to Russia.

Bout, a 43-year-old former Soviet air force officer, is reputed to be one of the world's most prolific arms dealers. He has allegedly supplied weapons that fuelled civil wars in South America, the Middle East and Africa, with clients including Liberia's Charles Taylor and the Libyan leader, Muammar Gaddafi, and on both sides of the civil war in Angola.

Shackled in leg irons, Bout cried after the verdict was read and hugged his wife and daughter.

"This is the most unfair decision possible," his wife said, speaking in Russian. "It is known the world over that this is a political case."

Bout says he is the victim of an American "frame-up." During testimony, he claimed he ran a legitimate air cargo business and was in Bangkok to discuss selling planes to Thai businessmen.

Bout's lawyer, Lak Nittiwattanawichan, also called the extradition politically motivated and said he would keep fighting it.

"I am going to submit a request to the ministry of foreign affairs and the cabinet," he said. "I will also submit a request to the king and queen."

Bout was arrested in March 2008 at a Bangkok luxury hotel as part of an elaborate sting in which US agents posed as arms buyers for the Revolutionary Armed Forces of Colombia (Farc), which Washington classifies as a terrorist organisation.

After his arrest, Bout was indicted in the US on charges of conspiring to sell millions of dollars worth of weapons to Farc, including more than 700 surface-to-air missiles, thousands of guns, hi-tech helicopters and planes fitted with grenade launchers and missiles.

The case became a diplomatic tug-of-war between Moscow and Washington.

Russia made great efforts to get Bout out of Thailand. Experts say Bout has been useful for Russia's intelligence apparatus, and Russia does not want him going on trial in the US.

In August 2009, the Bangkok criminal court rejected the extradition request. It said that Thailand considered Farc a political movement, rather than a terrorist group, and that extradition under a Thai-US treaty could not be granted for a political offence.

The appeals court disagreed, saying the case was not a political one and Bout should go to New York to answer to criminal charges.

"The court has decided to overturn [the lower court verdict]," the ruling said. "Now Viktor Bout would have to be extradited to the US within three months according to the extradition act."

Bout has never been prosecuted, despite being the subject of UN sanctions, a Belgian money-laundering indictment and a travel ban.

A US state department spokesman, PJ Crowley, said the Thai ambassador was summoned to the state department this week so that US officials could "emphasise that this is of the highest priority to the United States".

Thai prosecutors appealed the lower court's ruling on Washington's request. In February, US prosecutors filed new charges in the hope of convincing reluctant officials in Thailand to extradite Bout despite Russia's objections.

The new charges say Bout and a former business associate, Richard Chichakli, used a series of front companies to purchase two planes from US companies in 2007, in violation of US and UN sanctions. At the time, US officials intervened to block the sale.

Bout's nickname arose from his notoriety in the 1990s for running a fleet of ageing Soviet-era cargo planes to conflict hotspots in Africa. A high-ranking minister at the Foreign Office used the nickname in 2000 to single out Bout for his arms role in Africa.

The 2005 Nicolas Cage film, The Lord of War, is widely believed to be modelled on Bout's life.