Russia tested the readiness of its air defense systems deployed in the Crimean Peninsula it annexed from Ukraine back in 2014, amid joint military drills in the Black Sea by NATO countries and Ukraine, Interfax news agency reported Tuesday.

The Sea Breeze exercise, which began Monday, follows a rise in tensions between NATO and Moscow, which said last week it had fired warning shots and dropped bombs in the path of a British warship to chase it out of Black Sea waters off the coast of Crimea.

Russia’s Black Sea fleet was cited by Interfax as saying it had deployed around 20 warplanes and helicopters, including Su-24M bombers, as well as S-400 and Pantsir surface-to-air missile systems in the readiness tests.

Moscow considers Crimea part of Russia, but the peninsula is internationally recognized as part of Ukraine which wants it back.

"The Black Sea Fleet is doing a number of things to monitor the actions of ships from NATO and other countries taking part in Sea Breeze 2021," Interfax quoted the National Defence Management Centre as saying in a separate statement.

Moscow called for the Sea Breeze military exercises to be canceled before they began, and the Russian defense ministry has said it will react if necessary to protect national security.

Sea Breeze 2021 will last two weeks and involve about 5,000 military personnel from NATO and other allies, and around 30 ships and 40 aircraft. United States missile destroyer USS Ross and the U.S. Marine Corps will also take part.

Russia last week warned Britain and the U.S. against "tempting fate" by sending warships to the Black Sea and said it would defend its borders using all possible means, including military force.