The letter is addressed to Oleksiy Pokotylo, who is named as the Ukrainian "Head of the Department for National Security and Defense Affairs" and signed Tora Holst, Chief Prosecutor with the Stockholm International Public Prosecution Office.
The letter states that: "We assure you that any information which could pose a threat to Ukrainian interests or the international community shall be kept confidential and therefore every court session regarding this case will be held behind closed doors."
Holst, however, tells SvD that she did not write the letter and points out that it has the wrong letterhead.
It's still unclear who's behind the forgery, but Björn Palmertz, a senior analyst at the Swedish Defence University, believes it could be Russia.
"It's obvious that the letter aims to discredit both Sweden and the Ukraine while also implying that there are ties between the two countries," Palmertz says.