The Russian defense ministry says a US naval command ship has entered the Black Sea and the country’s navy has started tracking the vessel as tensions escalate over NATO activities near Russia's borders.
"The forces and means of the Black Sea Fleet have started monitoring the actions of the Mount Whitney command ship, which entered the Black Sea zone on November 4," TASS news agency quoted the Russian defense ministry as saying on Thursday.
The US navy confirmed that the USS Mount Whitney was in the region to conduct what it called routine maritime operations with NATO allies and partners.
On Monday, it said that the amphibious command ship had arrived in the Turkish city of Istanbul and would soon join forces with guided-missile destroyer USS Porter as well as other NATO ships in the Black Sea.
Russian President Vladimir Putin criticized the US-led NATO activity near Russia's borders and said his country's forces could observe the USS Mount Whitney "through binoculars or in the crosshairs of its... defense systems."
Putin and other top Russian officials have previously warned that the expansion of NATO activities in Ukraine represents a "red line" for Moscow.
On Tuesday, the Russian navy said in a statement that the Black Sea Fleet had rehearsed destroying mock enemy targets during drills in the sea amid the presence of US warships and NATO forces in the strategic region.
The Russian media also reported that the fleet’s air defense systems had been put on alert at its bases in the port city of Novorossiysk and on the Crimean Peninsula.
Kiev welcomes US move in Black Sea
However, the latest show of US military force was warmly welcomed by Ukraine, whose relations with Russia have in the past years turned sour over what it claims to be Moscow's "annexation" of Crimea and its backing for pro-Russia separatists in eastern Ukraine.
"Welcome, #USSMountWhitney. Ukraine has been calling for and strongly supports enhanced presence of our US and NATO partners in the region," Ukrainian Foreign Minister Dmytro Kuleba said on Twitter. "Additional 18,400 tons of diplomacy are surely helpful to this aim."
Russia has repeatedly accused NATO of carrying out provocative activities close to its borders as the US-led military alliance has expressed determination to reinforce the security of member states close to Russia.
Relations between Moscow and Kiev have been strained since clashes erupted in Ukraine's eastern Donbass region between Ukrainian government forces and ethnic Russians in 2014. The US, the European Union, and Ukraine claim that Russia has a hand in the conflict. Moscow strongly rejects the allegation.
The Black Sea peninsula of Crimea voted in a referendum to fall under Russian sovereignty in a referendum in the same year and more than 90 percent of the participants in the plebiscite voted in favor of that unification.