Two subversive groups that were planning a terrorist attack have been detained before the arrival of Ukrainian President Petro Poroshenko in Sloviansk, presidential press secretary Sviatoslav Tseholko has said, citing the head of state.

"President Poroshenko: two subversive groups that intended to commit a terrorist attack were detected 40 minutes before my arrival in Sloviansk. They were detained," Tseholko wrote on Twitter early on Wednesday.