KIEV, April 3. /TASS/. Ukraine’s State Bureau of Investigations has launched a criminal case against border guards and state aviation service employees over the recent flight to Moscow by two Ukrainian opposition leaders, the Ukrainskaya Pravda news portal reported on Tuesday.

Yuri Boyko, a presidential candidate and the founder of the Opposition Platform - For Life party, and chairman of the party’s Political Council Viktor Medvedchuk, travelled to Moscow on March 23, about a week before the first round of Ukraine’s presidential election. They held talks with Russian Prime Minister Dmitry Medvedev, focusing on Ukraine’s cooperation with Russia in the gas sector. Gazprom CEO Alexei Miller, who was attending the meeting, said that Gazprom was ready to start negotiations on direct supplies of gas for Ukrainian consumers.

According to information obtained from SBI sources, an investigation into suspected abuse of office was launched against officials, who cleared the aircraft for crossing the state’s aerial border.

"It is now being investigated whether granting permissions to this aircraft was legitimate. Those facts will be assessed from the legal point of view. The investigation continues," the portal quoted SBI sources as saying.

Ukraine’s chief prosecutor Yuri Lutsenko earlier vowed to launch a criminal case against Boyko and Medvedchuk for illegally crossing the state border, while Prime Minister Vladimir Groisman and Interior Minister Arsen Avakov said the matter should be investigated.

Meanwhile, a spokesman for the State Border Guards Service, Oleg Slobodyan, said border guards had no legitimate reasons to bar the opposition politicians from travelling to Russia.

"Inspectors of the State Border Guards Service permit citizens to cross the border after checking their documents. If the documents are valid and if a citizen has no travel restrictions imposed by other state agencies, he is free to cross the border," Slobodyan said.

Commenting on the reports, the Opposition Platform - For Life party described the investigation against border guards as the "agony" of the dying Ukrainian government.

"When Prosecutor General Yuri Lutsenko attempted to bring charges against Viktor Medvedchuk and Yuri Boyko, we described it as a ‘yet another manifestation of incurable dementia." This gut feeling proved to be totally right, because the launch of a criminal case against border guards and state aviation service employees can only be described as "the dementia keeps progressing." This is nothing but mortal agony of the outgoing government," the party said in a statement.