Story highlights The incident occurred on April 7 north of Poland in the Baltic Sea

U.S. says plane was in international airspace

Russia says it had transponder turned off and was flying toward Russia

(CNN) After a Russian fighter jet intercepted a U.S. reconnaissance plane in an "unsafe and unprofessional manner" earlier this week, the United States is complaining to Moscow about the incident.

Photos: Close encounters in the sky Photos: Close encounters in the sky UK Royal Air Force Typhoons, similar to this one seen in 2014, scrambled to intercept Russian bombers flying near British airspace, the British Defence Ministry said. It is one of the latest incidents in what NATO has said is an increase in Russian military flights near alliance members' territory. Hide Caption 1 of 7 Photos: Close encounters in the sky An American RC-135U, similar to this one, was intercepted by a Russian fighter jet earlier this month while flying in international airspace north of Poland. The U.S. crew believed the Russian pilot's actions were "unsafe and unprofessional due to the aggressive maneuvers it performed in close proximity to their aircraft and its high rate of speed," Pentagon spokesman Mark Wright said. Hide Caption 2 of 7 Photos: Close encounters in the sky British Royal Air Force jets intercepted this Russian Tu-95 Bear bomber in October. Hide Caption 3 of 7 Photos: Close encounters in the sky An F-15 Eagle from the 19th Fighter Squadron takes off at Joint Base Elmendorf-Richardson in Alaska. F-15 fighters intercepted Russian bombers off California in June. Hide Caption 4 of 7 Photos: Close encounters in the sky Fighter jets from the Netherlands intercepted two Russian bombers in Dutch airspace in April 2014. Hide Caption 5 of 7 Photos: Close encounters in the sky A Russian Air Force flight demonstration team performs with their Su-27 jet fighters over St. Petersburg, Russia. An Su-27 "showed its belly" to a U.S. reconnaissance jet in April 2014. Hide Caption 6 of 7 Photos: Close encounters in the sky A U.S. Air Force F-22 Raptor, top, escorts a Russian Air Force Tu-95 bomber off the coast of Alaska in 2011. Hide Caption 7 of 7

On Tuesday, a U.S. RC-135U was flying over the Baltic Sea when it was intercepted by a Russian SU-27 Flanker. The Pentagon said the incident occurred in international airspace north of Poland.

The U.S. crew believed the Russian pilot's actions were "unsafe and unprofessional due to the aggressive maneuvers it performed in close proximity to their aircraft and its high rate of speed," Pentagon spokesman Mark Wright said.

.To dispel rumors: US aircraft flying IAW ICAO flight rules in intl airspace was intercepted by Russian fighter in unsafe manner April 7.1/2 — U.S European Command (@US_EUCOM) April 11, 2015

Russian state news agency Sputnik reported the U.S. plane was flying toward the Russian border with its transponder switched off, according to a Defense Ministry spokesman. Maj. Gen. Igor Konashenkov said the Russian jet flew around the U.S. plane several times to identify it and get its tail number.

An official with the U.S. European Command said the claim that the transponder was off was false.

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