The Kiev office of the judge hearing the case of Russian citizens Alexander Alexandrov and Yevgeny Yerofeyev was attacked by arsonists on Thursday night, the rusnovosti.ru news website reported Friday.
The fire started as a result of an arson attack by unknown assailants who threw Molotov cocktails at at the Goloseevskiy district court building in Kiev.
Police said that a group of youths climbed over the court fence at night and threw the explosives, one of which broke through a third floor window, rusnovosit.ru reported.
Documents in his office were not damaged, according to the judge, Ukrainian media reported.
Aleksandrov and Yerofeyev were arrested in May 2015 in eastern Ukraine and further legal proceedings against them were scheduled for April 8. Ukrainian authorities claimed that the pair were Russian Main Intelligence Directorate fighters and accused them of terrorism.
The Russian Defense Ministry said at the time that the two were not active service personnel.