Russia will respond to Ukraine's latest attacks as and when its military sees fit, the Kremlin said on Thursday, accusing Kyiv of state terrorism and confirming that President Vladimir Putin had told Donald Trump that Moscow was obliged to retaliate.

Russian aircraft were damaged but not destroyed in a June 1 attack by Ukraine, and they will be restored, Russian Deputy Foreign Minister Sergei Ryabkov said in an interview with the state news agency TASS.

A Ukrainian military officer said Russian forces are preparing major advances lasting into next year as Moscow seeks to establish a buffer zone along the Ukraine-Russia border.