"I just found out that the extension of Daria Trepova's arrest is scheduled for today at 11:00 a.m. [08:00 GMT]," Gorbunova said.
In April, Russian military reporter Maxim Fomin, also known as Vladlen Tatarsky, was killed when an improvised explosive device that was snuck into a café in St. Petersburg exploded. Trepova was detained on suspicion of being behind the blast.
Russia's National Anti-Terrorism Committee said the Ukrainian special services and the supporters of the Russian non-profit Anti-Corruption Foundation (FBK, designated extremist organization and foreign agent, banned in Russia) masterminded the terrorist attack.