The Security Service of Ukraine (SBU) has opened a criminal case on a possible terrorist attack, public calls to commit terrorist attacks and the illegal making of explosives by members of a number of extremist political organizations.

"On August 23, the SBU's investigation department in Kyiv region opened a criminal case on preparations to commit a terrorist attack, under Articles 14 and 258 of the Criminal Code, for public calls to commit terrorist attacks under Article 258-2 of the Criminal Code and for the illegal storage and making of explosives under Article 263 of the Criminal Code," SBU spokeswoman Maryna Ostapenko said at a press briefing on Tuesday.

She said that in the premises owned by Vasylkiv City Council, SBU officers had found an object, which, after a respective examination was conducted, was described as an improvised explosive device packed with nails, bolts and metal objects. She said that bomb's blast radius could have been more 100 meters.

Ostapenko also said that the people detained in the premises were released on Tuesday morning, but that they were still suspects, as the investigation is continuing. She also said that all of the detainees were residents of Kyiv and confirmed that taking into account the materials seized from them, the detainees are related to such organizations as the Social National Assembly and Patriot of Ukraine.

"In addition to the explosive device, SBU officers also found a huge number of leaflets calling for extremist actions. The seized electronic medium containing a video showing schemes for blocking public institutions and producing improvised explosive devices, and one of the folders even contains videos of child pornography," Ostapenko said.

She described as "absolute nonsense" statements by the detainees in the media that they had nothing to do with the evidence and that the clues found were allegedly left by somebody in their premises.

As reported, SBU officers detained three members of what they said was an organized criminal group in the town of Vasylkiv, Kyiv region, on August 22. The SBU said the group intended to detonate a bomb during the celebration of Ukraine's Independence Day in Kyiv