Russia and Ukraine both conducted military exercises this week, according to a Wednesday report by Interfax.
Russia reportedly had fighter planes and ships practicing airstrikes and combating air attacks, while Ukraine also held military drills, Reuters reported.
"About 10 aircraft crews and ships of the Black Sea fleet's Novorossiysk naval base ... took part in this combat training event," Interfax reportedly wrote, citing Russia's Black Sea fleet.
Russia's Black Sea fleet also told the news outlet that Russia's Sukhoi fighter jets carried out training flights over Black Sea waters as they practiced how to respond to air attacks, Reuters reported.
Ukraine has expressed recent concerns over a possible Russian attack. Tensions between the two countries have increased as Ukraine has accused Russia of organizing troops nearby, which Russian officials have denied, the news outlet noted.
On Wednesday, Ukraine began strengthening its border with anti-tank and air units, Reuters reported.
Dmitry Peskov told state television on Sunday that the “hysteria” about Ukraine is “being built up artificially."
Earlier this week, U.S. intelligence showed that Russia has a buildup of troops and artillery along the border, a move that signals the country is prepared to push into Ukraine from multiple locations.