Colombia is to seek the extradition of an Israeli mercenary, convicted in absentia of training death squads, who has been arrested in Russia.
The AUC paramilitary group has been linked to the drugs trade
Yair Klein, a former Israeli colonel, was held at a Moscow airport on an international arrest warrant.
He was sentenced to 10 years for training drugs traffickers and right-wing paramilitaries in the 1980s.
Prosecutors say those trained went on to carry out some of the country's most notorious political assassinations.
"Colombia's government is going to make a formal petition to the Russian foreign ministry, so he is sent here to pay his sentence," Colombia's foreign minister Fernando Araujo told reporters.
The Russian authorities have refused to provide details about Klein's capture and have not commented on the extradition request.
Klein was convicted of training a cadre of killers for the Medellin drug cartel.
They later became the nucleus of the brutal right-wing paramilitary army known as the United Self Defence Forces of Colombia (AUC), says the BBC's Jeremy McDermott in Colombia.
The Colombian authorities say Klein was hired by the Medellin cartel of drug lord Pablo Escobar, which set up a training school for paramilitaries and assassins in Colombia.
Escobar was blamed for the deaths of thousands of people in his war against the state, including blowing up an airliner in 1989. He was finally tracked down and shot dead by police in Medellin in 1993.
The paramilitaries are thought to have murdered many thousands of people in their bloody rampage of the past 20 years, our correspondent says.
Klein was arrested and imprisoned in Sierra Leone in 1999 on charges of smuggling arms to the rebel group Revolutionary United Front.