"The Security Service of Ukraine, within its competence, in a short time will provide a legal assessment of the visit of Ukrainian citizens Yuriy Boyko and Viktor Medvedchuk to one of the leaders of the aggressor country and their statements," the SBU said in a Facebook statement.

Previously, Ukrainian presidential candidate Yury Boyko, following a meeting with Russian Prime Minister Dmitry Medvedev and Gazprom head Alexei Miller, said that negotiations with Moscow would continue.