President Vladimir Putin has called U.S. and NATO activities in the Black Sea a "serious challenge" for Russia, which has asserted additional naval rights in the region since seizing Crimea from Ukraine in 2014.
Putin's November 13 statements were the second effort by the Kremlin in less than 24 hours to highlight the Western military presence in the Black Sea region and accuse Washington of escalating tensions since media reports this week claimed U.S. officials were warning European allies of the risk of a possible Russian attack.
"The United States and its allies in NATO are carrying out unplanned exercises in the Black Sea," Russia said on the state's Vesta TV channel. "Not only is a rather powerful naval group involved in these exercises, but also aviation, including strategic aviation. This is a serious challenge for us."
It was unclear what exercises he was referring to, although NATO has carried out major Black Sea drills in the past four months or so.
WATCH: More than 30 vessels from 32 countries -- including NATO members -- took part in military drills in July co-hosted by Ukraine and the United States on the Black Sea.
U.S. officials last week raised alarm bells over Russian activities near Ukraine, where Moscow-backed separatists control swaths of territory in an ongoing seven-year conflict.
Secretary of State Antony Blinken warned Russia against making another "serious mistake" on Ukraine as Washington sought information about an alleged Russian troop movement near the border that the Pentagon called "unusual in its size and scope."
EU officials reiterated those concerns on November 12 and said they were monitoring the situation along with their U.S. and British allies.
France articulated its concerns and warned Moscow that any aggressive actions would have "serious consequences."
The warning came during talks in Paris in which French Defense Minister Florence Parly and Foreign Minister Jean-Yves Le Drian were meeting with their Russian counterparts, Sergei Shoigu and Sergei Lavrov.
Russia has insisted despite considerable evidence that it is not a party to the Ukrainian conflict.
Previous Russian troop buildups near the Ukrainian border have elicited concern before in Kyiv and among Ukraine's Western partners.
Tensions have also been ratcheted up around Ukraine by the Nord Stream 2 pipeline that will help Russia avoid transit through Ukraine with energy supplies bound for Western Europe.