Moscow, Russia - Russia warned the US on Friday that drone flights over the Black Sea raised the risk of "direct confrontation" between Moscow and NATO, days after the Kremlin blamed Washington for a deadly missile strike on Crimea.

Tensions between Moscow and Washington soared after the Kremlin accused Ukraine of attacking the Russian-annexed Crimean peninsula with a US missile on Sunday, killing four people, including two children.

On Friday, Russia's defense ministry said it had "observed an increased frequency of US strategic unmanned aerial vehicle flights over the waters of the Black Sea", which surrounds Crimea.

It said the drones were "carrying out reconnaissance" and providing information to Western-supplied Ukrainian weapons planning to strike Russian targets.

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"This demonstrates the increasing involvement of the United States and NATO countries in the conflict in Ukraine on the side of the Kyiv regime."

Such flights "increase the risk of a direct confrontation between the alliance and Russia" and the army has been instructed to prepare an "operational response", the defense ministry said.

The US routinely carries out drone flights over the Black Sea, operations that it says are conducted in neutral airspace and in accordance with international law.

In March 2023, Russia intercepted a US MQ-9 Reaper drone over the key waterway, an incident that heightened fears of direct confrontation between the two nuclear powers.

Russia has repeatedly warned Washington and the West they risk becoming "direct participants" in the Ukraine conflict by supplying Kyiv with weapons.

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Ukraine's attack on the Crimean port of Sevastopol on Sunday drew fury from Moscow, which called the strike a "bloody crime" by a Kyiv regime "armed by Washington."

Pentagon spokesman Major General Pat Ryder said Ukrainians made "their own decisions" about where to strike, while the State Department pointed out Crimea is recognized internationally as part of Ukraine.

Russia nonetheless vowed there would be "consequences" and summoned US ambassador Lynne Tracy in protest.