Russian bombers came within one nautical mile of the U.S. Navy aircraft carrier USS Ronald Reagan earlier this week off Korea, prompting the nuclear-powered vessel to scramble fighter jets, a 7th Fleet spokeswoman told Stars and Stripes Thursday. The giant Tupolev bomber aircraft, also known as the Bear, flew as low as 500 feet as it approached the Reagan, which had been conducting scheduled maneuvers with the South Korean navy.

As the two Tupolevs approached, the Reagan launched four F/A-18 Super Hornet fighter jets to intercept and identify, a standard procedure when encountering unidentifiable aircraft, said Lt. Lauren Cole.

While the USS Ronald Reagan sent up four combat aircraft to deal with the two bombers, the entire incident took place in international waters, making the approach completely legal if not somewhat provocative and potentially dangerous.

“We are advocates of any country being able to operate within international norms,” Cole said. “We do caveat that with the fact that all of these operations need to be conducted in accordance with the rights and regulations of other countries, and within a safe manner.”

Russian aircraft have made a habit over the last year of testing international boundaries by violating the airspace of other countries and approaching U.S. and NATO ships in what the U.S. have previously described as “provocative” action.

During a similar incident in April last year, the USS Donald Cook witnessed a Russian SU-24 fighter jet make 12 “close-range, low-altitude” flybys while the ship was conducting exercises in the Black Sea near Romania, according to the Pentagon. Last month, Turkey accused Russian jets of infiltrating its airspace while it conducted bombing missions inside Syria.

The U.S. has been exercising freedom of international waters this week; the USS Lassen sailed through U.N.-recognized international waters that China had claimed as its sovereign territory.