Moscow (CNN) -- Russia criticized the United States on Friday for handing down a 25-year sentence to Russian arms dealer Viktor Bout, saying the verdict against him was "baseless and biased."
Bout, who denies wrongdoing, was sentenced Thursday to 25 years behind bars by a federal judge in New York.
Bout, who was dubbed "the merchant of death" by his accusers, was convicted last year on four counts of conspiracy to kill Americans, acquire and export anti-aircraft missiles and provide material support to a terrorist organization.
Russia's foreign ministry accused the United States of acting illegally when its agents arrested Bout in Thailand and of pursuing a political agenda after he was extradited to the United States to face trial.
In a statement, Russia accused the United States of seeking a forced confession by "creating intolerable conditions of detention, physical and psychological impact."
In addition, the Russian foreign ministry said, U.S. authorities also encouraged a media campaign against Bout, which was bound to influence the jury.
The foreign ministry will do everything it can to bring Bout back to Russia, its statement said.
Bout had faced the possibility of life in prison at his sentencing hearing in Manhattan.
"Viktor Bout has been international arms trafficking enemy number one for many years, arming some of the most violent conflicts around the globe," said Preet Bharara, the U.S. attorney in Manhattan.
"He was finally brought to justice in an American court for agreeing to provide a staggering number of military-grade weapons to an avowed terrorist organization committed to killing Americans."
At the trial, the prosecution said that during a 2008 sting operation by U.S. drug enforcement agents in Thailand, Bout believed he was selling weapons to Colombian guerrillas.
Bout continued to declare his innocence Thursday.
"I am not guilty," he said through a translator. "I never intended to kill anyone. I never intended to sell any arms to anyone. God knows this is the truth."
Bout's wife, Alla, said after the hearing that her husband "said few words" in reaction to the sentence. He and his lawyer did not regard the case as lawful, she did.
His lawyer, Albert Dayan, filed a letter last week asking Judge Shira A. Scheindlin, who presided over the trial and who set Bout's sentence, to set aside the guilty verdict.
Dayan urged the judge not to "become an unwilling party" in what he called a "wrongful prosecution" for "purely political reasons." He argued that the conviction is a "product of malice" and that Bout has been an "object of private politics" coming from Washington.
The lawyer claimed that Bout was picked out by the United States government and lured into a crime manufactured by the U.S. Drug Enforcement Administration, in which the agency played "the role of judge, jury and executioner. "
In his claim, Dayan insisted that Bout did not intend to sell any arms to the agents, that he had not sold any arms for several years and that the only thing he wanted to sell were two cargo airplanes, worth $5 million. Dayan stood by the claim that DEA officers baited his client into illegal activities.
"I do not profess, I do not argue that he's an angel, but he is innocent of these charges," Dayan wrote. "I felt it was my duty to speak out and let the world know."
According to a federal indictment, Bout was suspected of creating front companies that used his planes to deliver food and medical supplies, as well as arms.
After a sting operation in 2008, he was arrested in Thailand and in 2010 was extradited to the United States following a protracted court proceeding.
He was convicted in November after a three-week trial in New York.
Before his arrest, the DEA had struggled to draw Bout out of his Russian homeland, which is long thought to have sheltered and defended him.
Undercover agents met with Bout's associates the world over, from Curacao to Copenhagen, in an attempt to set up a meeting with their target, according to the indictment.
The Russian businessman also has been accused of assembling a fleet of cargo planes to traffic military-grade weapons to conflict zones around the world since the 1990s.
Allegations of trafficking activities in Liberia prompted U.S. authorities to freeze his American assets in 2004 and prohibited U.S. transactions with him, according to the indictment.
Bout has maintained that he operated legitimate businesses and had acted as a mere logistics provider. His exact age is unclear, but he is believed to be in his late 40s or 50s, with his age in dispute because of different passports and documents.
The U.S. attorney's office said it had no confirmed age.
Critics have accused Bout of providing arms to rebels in several countries and fueling bloody conflicts in places such as Liberia and Sierra Leone.
In 2000, then-British Foreign Office official Peter Hain branded him "Africa's chief merchant of death" at a time when Bout is believed to have supplied arms to officials in Sierra Leone, a former British colony then embroiled in civil war.
CNN's Zarifmo Aslamshoyeva contributed to this report.