Erdogan's comments came as NATO leaders huddled in Washington and Kremlin spokesman Dmitry Peskov said that Russia was planning "response measures" to contain the "very serious threat" from the alliance.

"The possibility of a direct conflict between NATO and Russia is undoubtedly worrying," said Erdogan, who is in Washington for a NATO summit. "Any steps that could lead to this outcome should be consciously avoided."

Erdogan spoke a day after NATO allies announced they had started transferring F-16 jets to Ukraine while stepping up promises to Kyiv on eventual membership in the alliance, at a 75th anniversary summit clouded by political uncertainties in the United States.

On the eve of the summit, Russia fired a barrage of missiles on Ukraine, killing dozens, including in Kyiv where a children's hospital was heavily damaged

Peskov, in comments published by Russian news agencies also said the Western military alliance, which is holding a summit in Washington this week, was now "fully involved in the conflict over Ukraine".

A member of NATO, Turkey has sought to balance ties between its two Black Sea neighbours Russia and Ukraine since Moscow's full-scale invasion.

Ankara has sent drones to Ukraine while shying away from Western-led sanctions on Moscow.