Russian MPs say the charges Mr Bout faces are politically motivated
A hearing has begun in a Bangkok court to determine if alleged Russian arms dealer Viktor Bout should be extradited to the United States.
Mr Bout was detained in a sting operation in Bangkok on 6 March, in which US agents posed as arms buyers.
He has been indicted on four terrorism charges in the US and has been accused of supplying al-Qaeda.
Dubbed "the Merchant of Death" by the media, Mr Bout denies any illegal activities.
His extradition hearing opened in Bangkok's Criminal Court on Monday after months of delays.
Mr Bout has had trouble retaining a defence team - the first lawyer said he had problems with his heart, the second failed to appear, and a third has now been assigned by the court.
The new defence lawyer Preecha Prasertsak tried to block the extradition hearing by arguing Mr Bout's detention in Thailand was illegal, but the court ruled it would discuss that issue at a later date.
'Lord of War'?
Mr Bout, aged 41, faces charges of conspiring to kill Americans, conspiring to kill US officers or employees, conspiring to provide material support to terrorists and conspiring to acquire and use an anti-aircraft missile, according to a US indictment made public on 6 May.
He faces a life sentence if found guilty.
American prosecutors arguing for the right to try Mr Bout in the US say he was picked up after a sting operation, which was covertly recorded, featuring US agents posing as members of the Revolutionary Armed Forces of Colombia, or Farc.
His sales pitch allegedly included the offer of more than 700 surface-to-air missiles and airplanes outfitted with grenade launchers and missiles. The US classifies Farc as a terrorist organisation.
Mr Bout has been accused of breaking several United Nations arms embargoes, and of having clients ranging from African dictators and warlords to the Taleban and al-Qaeda.
The Russian news agency Itar-Tass reports from Bangkok that Mr Bout - whom it described as a businessman - had arrived in Thailand as a tourist.
"It is noteworthy that the Russian was detained in an American-led sting operation," the Russian news agency said.
The State Duma - the lower house of Russia's parliament - on Friday adopted a statement in support of Mr Bout, Itar-Tass reports.
"Political motives, attempts to link this issue with the fight against international terrorism and thus damage the interests and reputation of Russia, are present in Bout's case", claimed the parliamentarians in the statement.
"It is necessary to intensity efforts aimed at securing the rights of Russian citizen Viktor Bout, prevention of his illegal prosecution and return to his home country, as well as at curbing attempts to use this case against Russia," the lawmakers said, according to Itar-Tass.