(CNN) In a still publicly unacknowledged incident, a Russian military surveillance aircraft flew close to four NATO warships in the Baltic Sea on Thursday, including the destroyer USS Jason Dunham, which captured video of the incident, a U.S. Defense Department official said Saturday.

The Pentagon has not released the video. The Russian plane was a Russian Maritime Patrol aircraft, similar to the U.S. P8. The official said the Dunham was part of a four-ship group that also included British, French and German warships. At one point, the Russian aircraft flew above the deck of one of the NATO ships at an altitude of just 500 feet.

"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.

The official added that none of the warships felt directly threatened by the Russian overflight, but the flight was "lower and closer" than the U.S. had routinely seen.

Read More