The head of the FBI has strongly criticised the Scottish government for freeing convicted Lockerbie bomber Abdel Basset al-Megrahi.
Megrahi, 57, who has terminal cancer, was released on compassionate grounds on Thursday. He was greeted by cheering crowds at Tripoli airport on his return to Libya.
The former Libyan agent is the only person convicted of the 1988 bombing that killed 270 people. He was given a life sentence in 2001 and lost an appeal in 2002, though a review board ruled in 2007 that there might have been a miscarriage of justice.
Federal Bureau of Investigation director Robert Meuller has published a letter addressed to the Scottish Justice Secretary, Kenny MacAskillon, on the FBI website.
"Your action in releasing Megrahi is as inexplicable as it is detrimental to the cause of justice," the letter reads.
"Indeed your action makes a mockery of the rule of law. Your action gives comfort to terrorists around the world who now believe that regardless of the quality of the investigation, the conviction by jury after the defendant is given all due process, and sentence appropriate to the crime, the terrorist will be freed by one man's exercise of "compassion."
"Your action rewards a terrorist even though he never admitted to his role in this act of mass murder and even though neither he nor the government of Libya ever disclosed the names and roles of others who were responsible."
The Scottish government said it had consulted widely in the US and UK and had made the right decision, the BBC reports.