US spy planes have twice tried to approach the Russian border over the Black Sea with their transponders off, the Russian Defense Ministry said, adding that SU-27 fighter jets were scrambled in response.

“On September 7, the US P-8 Poseidon surveillance airplanes tried to approach the Russian border twice… with their transponders off,” Russian Defense Ministry’s spokesman, Major General Igor Konashenkov said in a statement.

The SU-27 fighter jets that intercepted the US aircraft were acting “in strict accordance with international flight rules,” the statement reads.

'Hazard of collision': US spy plane flew too close to passenger jets near Russian border – MoD https://t.co/kR65YvqKXa — RT (@RT_com) May 24, 2016

Two unnamed US defense officials earlier accused Russian jets of carrying out an “unsafe and unprofessional” intercept of the US spy aircraft, which was on a “regular patrol” over the Black Sea. The officials were speaking of the incident with Reuters.

They said the Russian SU-27 came within about 3 meters of the US plane, and the standoff lasted for about 19 minutes.

All Russian warplanes will fly over Baltic with transponders on, if NATO does the same https://t.co/gDF9sztWbXpic.twitter.com/HeMUgdPoob — RT (@RT_com) July 3, 2016

"They're up there for 12 hours and there are lots of interactions. But only one of the incidents was what the pilot determined was unsafe," a US official told Reuters.

The Russian Defense Ministry said that after the Russian jets approached the US spy planes close enough to visually identify them, the American aircraft sharply changed direction and flew away from the border. The ministry added that it was just the latest attempt by US aircraft to approach the Russian border close to the region where the massive Caucasus-2016 drills are being held.

The ministry stressed that there is no need for such actions, as it already officially invited military attaches from 60 countries, including NATO members, as well as more than 100 foreign journalists, to attend the final stage of the drills.

Pentagon claims Russian jet fighter barrel rolled within 25 feet of US reconnaissance plane https://t.co/aASQkaenf0pic.twitter.com/CRRL1mxNmy — RT (@RT_com) April 30, 2016

The Pentagon has told RT that its Navy P-8A Poseidon was conducting “routine operations in international airspace” when “a Russian SU-27 Flanker made an unsafe close-range intercept” at about 11:20 a.m.

“These actions have the potential to unnecessarily escalate tensions between countries, and could result in a miscalculation or accident which results in serious injury or death,” the US Defense Department said, stressing that most interactions US Navy aircraft and ships have with Russian units are “safe and professional.”

“We have concerns when there is an unsafe maneuver,” the Pentagon said.