Unknown persons threw bottles filled with a flammable liquid into the premises of Kyiv's Holosiyivsky District Court last night, causing a fire at the office of the judge who is presiding over the trial of Russian intelligence officers Yevgeny Yerofeyev and Alexander Alexandrov.

The case files have not been damaged.

The press service of the Ukrainian National Police department for Kyiv reported on Friday that at around 3:00 a.m. police received an alert that a group of young people had climbed over the fence around the Holosiyivsky Court building and had thrown bottles filled with a flammable liquid, one of which smashed a window on the third floor.

The office of the judge presiding over the Russian citizens' trial was partially damaged in the fire.

"According to the judge, the documents as part of these criminal cases were not damaged. Law enforcement agencies are considering several theories behind the offense. The main one of them is the judge's professional activities," the deputy chief of the National Police department in Kyiv, Oleksandr Pyvovar, said.

A local security guard called the police and State Emergency Situations Service rescuers immediately after the incident.

Investigators from the National Police central and district departments examined the scene and confiscated fragments of the bottles containing an unknown liquid. They were sent for examination. However, the fire damaged office equipment and furniture.

The investigative unit of the Holosiyivsky district police department entered information into the Unified Register of Pre-Trial Investigations under Part 2 of Article 378 of Ukraine's Penal Code (intentional destruction or damage of property owned by a judge, a people's assessor or a juror). Search and investigative measures are being taken as part of the inquiry in order to identify and detain the suspects. Police officers are again examining the scene.

For his part, Ukrainian Deputy Prosecutor General and Chief Military Prosecutor Anatoliy Matios told reporters that the office into which a bottle with a flammable liquid was thrown was destroyed by fire completely along with the documents kept there. However, security measures were taken with regard to the files as part of the Russian citizens' case, and these documents were not damaged.

Matios also stressed that a session in the case of Yerofeyev and Alexandrov, set for Friday, will go ahead.

He described the recent incident as a factor of "both pressure and intimidation."

"The series of controversial and tragic events linked with this case continues," he added.