Ukrainian President Petro Poroshenko has summoned his top brass to discuss the latest flare-up in tensions between Moscow and Kiev. Military units positioned in Ukraine's eastern Donbass region and just north of Crimea have been put on high alert.

Taking into account recent events, I have ordered Ukraine's army forces, national guard, and security service personnel to be on the highest level of combat readiness. Border guards should pay special attention to our administrative border with Crimea," Viktor Muzhenko, commander-in-chief of The Armed Forces of Ukraine, said.

The presidential announcement comes after Russia accused Kiev of organizing attacks in the annexed Crimean peninsula. Kiev has denied the allegations and accused Russia of trying to stir up tensions in the region. Russian President, Vladimir Putin has also met with Russian security chiefs to discuss "additional measures for ensuring security for citizens and essential infrastructure in Crimea."