Yuriy Boiko, Viktor Medvedchuk, Dmitry Medvedev
© Yekaterina Shtukina (TASS)The legislation has been introduced following a meeting between Ukrainian presidential candidate Yuriy Boiko (center) and tycoon Viktor Medvedchuk (right) with Russian Prime Minister Dmitry Medvedev (left) and Gazprom's CEO Aleksei Miller.
The Ukrainian government has banned unscheduled flights to Russia after a recent visit to Moscow by two opposition politicians.

The action was initiated by Ukrainian Interior Minister Arsen Avakov, who said on April 3 that presidential candidate Yuriy Boiko and Opposition Platform -- For Life party official Viktor Medvedchuk had "used a loophole in Ukraine's legislation" to take a direct flight to Moscow last month.

Avakov said the ban would not apply to potential flights arranged for international organizations such as the Organization for Security and Cooperation in Europe (OSCE), the United Nations, and the Red Cross.

Ukrainian Prime Minister Volodymyr Hroysman said "these restrictions will remain in place until Russia... ceases to be an aggressor country and turns into a civilized state."

Ukrainian Prosecutor-General Yuriy Lutsenko said a probe will be launched into the two opposition politicians' "illegal border crossing" when they flew to Russia on March 22, where they met with Russian Prime Minister Dmitry Medvedev and Aleksei Miller, the CEO of Russian energy giant Gazprom, with whom they discussed ways to restore trade and economic ties.

Direct flights between the two countries were stopped in October 2015 amid a standoff over Moscow's annexation of Ukraine's Crimean Peninsula and its support for separatists in eastern Ukraine in 2014.