As reported by Censor.NET citing 112 Ukraine, this was announced by SBU Head Vasyl Hrytsak.
"It is this detention facility that could have been bombed under order of Russia's GRU. We have recorded a conversation of persons who made reconnaissance of this facility, where they say "there are separatists there," "someone else is there, no problem," "we'll have a car full of explosives and blow it up," etc. They planned to attack this very jail," he noted.
"We've unclassified this conversation so that people can see what Russia's GRU officers are involved into," Hrytsak said.