Another suspect, who is a former Party of Regions parliamentarian, Volodymyr Medianyk, has been arrested as part of an inquiry against the party's former parliamentary faction leader, Oleksandr Yefremov, Ukraine's Prosecutor General Yuriy Lutsenko wrote on his Facebook page.

"The Ukrainian Prosecutor General's Office has arrested the following suspect as part of the Yefremov case: former Party of Regions deputy Volodymyr Medianyk. Our petition for his detention will be considered by Pechersky court at 9 a.m. on Monday," the prosecutor general said.

Yefremov was arrested on July 30 on suspicion of encroaching on Ukraine's territorial integrity.

He was held at Boryspil Airport with a ticket to Vienna.

Yefremov is suspected of having committed a number of criminal offences: misappropriation; performing intentional acts with the aim to alter Ukraine's borders in breach of the Constitution, resulting in people's deaths and other serious consequences; and providing other assistance in the creation of a terrorist organization (Part 5 of Article 191, Part 1 of Article 110 and Part 1 of Article 258-3 of the Criminal Code, respectively).

On July 1 Kyiv's Pechersky court remanded Yefremov in custody for 60 days until September 28.

Yefremov's defense lawyer said they will appeal his arrest once the court ruling has been read out in full.