A U.S. Navy destroyer fired warning shots at five Iranian boats Sunday near the Strait or Hormuz, defense officials told CNN on Monday.
The USS Mahan was traveling along the narrow strait, en route to the Persian Gulf when the Iranian boats quickly approached.
That's when the USS Mahan fired warning shots, along with using radio calls, flares, bells and whistles to warn off the ships.
Davis said there have been about 35 similar encounters that the Navy "assessed to be unsafe and unprofessional." He added that most of the incidents happened in early 2016.
Sunday's incident is just the latest in a series of tense encounters between the U.S. and Iran.
Although it's rare for an American ship to fire warning shots, in August 2016 the USS Squall fired warning shots at a speeding Iranian boat that came within 200 yards of the ship.
In September 2016, Iran threatened to shoot down two U.S. Navy surveillance aircraft that were flying over the Strait or Hormuz.
Iran made three radio calls to the U.S. aircraft, warning them not to enter the country's airspace, which reaches 12 miles into the sea.
Although it's unclear how Donald Trump's administration will react to Iran, during a September campaign event the president-elect said Iranian boats "will be shot out of the water" if the aggression continues.