It was in a five-star Bangkok hotel, where he was expecting to meet Colombian Farc rebels at the closing stages of a multi-million dollar arms deal, that Bout was finally nabbed, ending a 12-month undercover operation.

It was by infiltrating Bout's innermost circle that agents from the United States Drug Enforcement Administration were able to get close to the former Soviet air force officer and finally bring him into custody.

'We were able to infiltrate his criminal organisation, to gain access to some of his key associates,' a DEA official said, asking not to be named.

'And from these key associates in numerous places throughout the world, undercover-type scenarios, we were able to introduce human cooperating sources into these key associates,' the official explained.

He added that the operation had involved a significant number of DEA agents and their counterparts around the world.

Bout has been linked to civil wars in Africa, Afghanistan's Taleban, Osama bin Laden's Al-Qaeda network and Marxist rebels in South America, earning him the nickname from one British minister of the 'Merchant of Death'.

Undercover agents first got close to Bout and an associate Andrew Smulian in February 2007, recording during a series of telephone calls and e-mail conversations in which the pair allegedly agreed to supply weapons.

In a series of meetings from the Netherlands Antilles to Romania, Smulian allegedly told undercover agents posing as Colombian Farc rebels that Bout had 100 surface to air missiles available and could also provide helicopters.

He allegedly said Bout could also provide armour-piercing rocket launchers and arrange to have the weapons dropped into Colombian territory using combat parachutes for a charge of five million dollars.

In between the meetings, Smulian is alleged to have discussed the deal with Bout over a cell phone provided by the undercover agents, while Bout allegedly told Smulian the weapons were ready to be delivered.

It was during their last such arranged meeting on Thursday that Bout was arrested. It was not immediately known if Smulian was in custody or on the loose or cooperating with prosecutors, who declined to comment on his exact status.

Both Bout and Smulian face charges of conspiracy to provide material support or resources to a designated foreign terrorist organisation and face up to 15 years in jail if extradited to the United States and convicted. -- AFP