Its statement was released with details expected of a phone call between Ukraine leader Volodymyr Zelensky and US President Joe Biden, who is reiterating support to Eastern European countries concerned about Russia's military plans.

The defence ministry said it had ordered three of its Su-27 fighters to deploy over the Black Sea "to identify air targets and prevent the violation of the state border of the Russian Federation".

The ministry said its crews had identified French Mirage 2000 and Rafale fighters, US CL-600 Artemis and RC-135 reconnaissance aircraft and a French KC-135 refuelling aircraft.

It said the French and American planes had reversed course once the Russian jets deployed and that the Western aircraft had not crossed the Russian border.

On Wednesday, Russia said it had dispatched planes to escort three French military planes flying near its borders in the Black Sea.

The defence ministry said its pilots again escorted French Mirage 2000 and Rafale jets after stopping them from violating the Russian border.

That incident followed another last week when Russia said a "catastrophe" was avoided when a Russian passenger plane dived to avoid a NATO reconnaissance aircraft that crossed its path above the Black Sea.

Western and Ukrainian officials say they currently fear Russia -- which already seized Ukraine's entire Crimea region in 2014 and backs a large-scale separatist force in the east -- is preparing an even larger scale invasion.

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