The weapons, which have been used in Syria, are capable of shooting down enemy jets and airliners.
Ukraine has been holding military exercises in southern Ukraine since Wednesday, involving its fleet of warplanes, which the spokesman for Ukraine’s General Staff insisted was pre-planned.
The deployment of the S-400 comes two days after Ukraine’s president ordered the country’s military to be on its highest war footing in preparation for a conflict with Russia.
Petro Poroshenko instructed all military units near Crimea and in the eastern region of Donbass to be at the highest level of combat readiness after an escalation of hostilities in the last 24 hours.
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