President Vladimir Putin has ordered the Federal Security Service's (FSB) Border Service to take all possible measures to tighten the Russian-Ukrainian border's security and rule out its illegal crossing, Russia's presidential press service reports.
No other details are available at the moment.
The directive comes just hours after the swearing-in in Kyiv of new Ukrainian President Petro Poroshenko.
It also comes a day after Putin held talks with global leaders in France, where U.S. President Barack Obama called on him to cease support for separatists in eastern Ukraine and stop the provision of arms and material across the border.
Kyiv said on June 5 that three of its border posts had been seized by separatists.