The U.S.S. Jason Dunham, an American guided missile destroyer, participated in military exercises with the Latvian navy over the weekend, according to a Russian media report. The United States has recently reaffirmed its alliance with the ex-Soviet Baltic states of Latvia, Lithuania and Estonia against Russian threats in Eastern Europe.

The guided missile destroyer arrived in the seaside capital of Riga and took part in drills aimed at improving cohesion between the U.S. and Latvian naval forces, Russian-owned Sputnik News reported. The same vessel previously visited neighboring fellow NATO member Estonia and Finland, which has been strengthening its ties to the alliance amid a marked increase in Russian military activity. Moscow seized the formerly Ukrainian territory of Crimea in March 2014 and has also been accused by the international community of supporting pro-Russian rebels in eastern Ukraine.

The Jason Dunham “is conducting naval operations in the U.S. 6th Fleet area of operations in support of U.S. national security interests in Europe,” according to the ship’s Facebook page. Sputnik, which is state-owned, said the Kremlin viewed the ship’s activity as “blatant saber-rattling.”

A Russian military aircraft “buzzed,” or flew over, the guided missile destroyer and three other NATO vessels last week, a U.S. Defense Department official told CNN. The aircraft dropped to an altitude of about 500 feet during the incident, which the official described as a “routine” occurrence.

“We are not calling this safe and professional. We are calling it routine, but we are on the edge of being very uncomfortable," the official said.

Last month, the Pentagon announced plans to station hundreds of pieces of heavy weaponry, including tanks and howitzers, in several Eastern European NATO member nations that used to be under Russian domination. The decision was made to demonstrate America’s commitment to defending its allies in the region, Defense Secretary Ash Carter said.