Russia's Defense Ministry has protested a U.S. reconnaissance flight over the Sea of Japan near the nation's borders, saying it jeopardized air safety in the area.

The ministry said in Monday's statement that it summoned a U.S. military attaché to indicate that the U.S. crew's "unprofessional" action "raised the danger of collision with civilian carriers' planes."

It said that the U.S. RC-135 plane was flying with its transponder switched off and the U.S. failed to give information about the flight to air traffic controllers. The ministry said the U.S. aircraft was flying at an altitude used by regular civilian flights in the area.

The ministry urged the U.S. to take relevant measures to "avoid the repetition of such situations."

There was no immediate response from the Pentagon to the Russian complaint.