The U.S. is protesting an intercept of a U.S. reconnaissance plane by a Russian fighter jet last week, calling it "unsafe and unprofessional" amid what it views as increasingly aggressive air operations by Moscow.

Pentagon spokesman Mark Wright on Sunday said the U.S. was filing a complaint to Russia after the April 7 incident over the Baltic Sea. Russian officials have denied their pilot did anything wrong, according to several news reports.

According to the Pentagon, the U.S. RC-135U plane was flying in international airspace north of Poland. U.S. officials say a Russian SU-27 fighter intercepted the U.S. aircraft at a high rate of speed from the rear, and then proceeded to conduct two more passes using "unsafe and unprofessional maneuvers" in close proximity.

It isn't the first time the U.S. has protested to Moscow what it considered to be an unsafe intercept. Last April, a Russian fighter jet intercepted a U.S. reconnaissance plane in international airspace over the Sea of Okhotsk.

—The Associated Press