Moscow has accused the United States of putting civilian lives at risk after a reported mid-air near-miss on Friday, involving two civilian aircraft and a NATO reconnaissance plane.

Russia's foreign ministry specifically accused the US Air Force of creating a "threat to civil aviation" over the Black Sea.

"Just because an air incident over the Black Seas' Int waters has been prevented, this does not mean the US and NATO can further put lives at risk with impunity," Russian Ministry of Foreign Affairs spokeswoman Maria Zakharova was quoted as saying on Twitter.

What does Russia say happened?

According to Russia's Federal Agency for Air Transport, a NATO CL-600 surveillance plane was flying over the Black Sea international waters on the morning of December 3. The aircraft was observed making a rapid descent from 11,000m to 9,200m, which allegedly crossed the designated path for civilian aircraft.

The reconnaissance aircraft's crew did not respond to Russian air traffic control, according to the Russian agency.

At that moment a Russian Aeroflot Airbus A330-300 flying from Tel Aviv to Moscow and a CL-650 plane belonging to Malta flew along their designated flight paths. It's understood that the two aircrafts' travel paths had to be promptly changed to allow them to continue safely.

Russia said that flights by military aircraft with no form of radio communications presented a risk to civilian planes in the Black Sea region, and that it would lodge a diplomatic protest. The statement was posted in full on the ministry's Facebook account.

US, Russia eye each other with mistrust

The reported incident comes amid claims that Russia is massing troops at the border with Ukraine. Kiyv has expressed concern that the troop build-up could lead to some form of escalation as soon as January, 2022.

US media outlets including the AP news agency and the Washington Post have reported US intelligence claiming to have evidence that Moscow is planning a military offensive. According to the reports, it could involve an estimated 175,000 Russian military personnel.

Moscow has denied the claims and has accused NATO of failing its peacekeeping commitments by refusing to de-escalate tensions.

US President Joe Biden and Russian President Vladimir Putin are due to hold an online meeting on Tuesday.

kb/dj (AFP, dpa)