Meanwhile, protesters are trying to break through the police cordon.
An associate of the New Forces Movement led by ex-Georgia President Mikheil Saakashvili, Severion Dangadze, has been detained attempting to flee Ukraine. Some of them clashed with security officers.
Mr Saakashvili's supporters tried to stop the police van taking him from leaving.
National Guard riot police were dispatched to help the SBU release the van but they soon found themselves surrounded by a crowd of protesters. Footage from the scene showed Saakashvili being taken away while several hundred protesters were blocking the road.
On Tuesday, the former president of Georgia and ex-governor of Ukraine's Odessa Region confined himself to the roof of his house in Kiev, while security forces searched his flat.
Ukraine is not considering extraditing former Georgian President Mikheil Saakashvili because his detention on Tuesday is related to alleged crimes against Ukraine, General Prosecutor Yuriy Lutsenko said in a press conference. But he quit in 2016, complaining that his efforts to root out corruption suffered official obstruction. Saakashvili criticized Poroshenko and the government for hesitant and obstructed anti-corruption drive and reform process in the country. "He is suspected of violating Article 110 of Ukraine's Criminal Code (treason) and Article 256 (assisting members of a criminal organization and hiding its criminal activity)", the PGO chief said.
In September, Saakashvili forced his way into Ukraine despite a police blockade created to keep him out.
Ukrainian Prosecutor General Yuriy Lutsenko has said that Mikheil Saakashvili, the leader of the Movement of New Forces party, has received half a million USA dollars from Ukrainian businessman Serhiy Kurchenko in order to organize protest rallies.