Tom Vanden Brook

USA TODAY

WASHINGTON — A Russian fighter jet buzzed a U.S. Air Force spy plane this week over the Black Sea, a risky maneuver that threatened the safety of the American crew, according to the Pentagon.

The incident occurred Jan. 25 when a Russian Su-27 intercepted a Air Force RC-135 that was flying in international airspace over the Black Sea. The Pentagon called the maneuver “unsafe and unprofessional.”

Russian military flights near NATO allies in that region have spiked in the past two years, NATO Secretary General Jens Stoltenberg told reporters in Brussels this week. NATO has matched that by intercepting Russian aircraft hundreds of times.

“We have visibly increased NATO’s presence in the eastern part of our alliance,” Stoltenberg said. “Over the last two years, Russian air activity close to NATO’s European airspace has increased by around 70%. In response, allied aircraft scrambled over 400 times to intercept Russian aircraft.”

The buzzing of the Air Force reconnaissance plane this week echoes incidents in the past few years in which Russian planes flew close to American aircraft, at times provocatively flashing weapons.

At the same time, U.S. and Russian officials continue to hold talks on avoiding conflict over battlefields in Syria. On Thursday, top Defense Department officials conducted a videoconference with their Russian counterparts on a “memorandum of understanding” regarding flight safety in Syria.

The U.S.-led coalition has been striking Islamic State targets in Syria since September 2014. Last year, Russian aircraft began flying combat sorties from their base in western Syria. Most of those attacks, the Pentagon maintains, have been directed against opponents of Syrian President Bashar Assad, who has plunged the country into a civil war that has killed hundreds of thousands. In October, the two sides agreed to maintain communication in order to avoid a conflict there.

Thursday’s conference focused on the safety of air crews, avoiding accidents and “unintended confrontation between coalition and Russian forces whenever the two sides operate in close proximity,” Pentagon press secretary Peter Cook said.

“The conversation was constructive and the two sides agreed to continue safety discussions in this format in the future,” Cook said.

On Friday, U.S. and coalition aircraft, including drones, conducted 16 airstrikes against Islamic State targets in Syria, the military announced Saturday.