Officials say Russian jets repeatedly intercepted U.S. naval reconnaissance planes over the Black Sea, and U.S. defense officials have complained a Russian pilot at one point flew within 3 meters of one of the planes.
The September 7 incident over the Black Sea was the latest in a series of near-miss encounters involving Russian planes and U.S. military ships and planes.
It also came as Russian ramped up large-scale military exercises involving thousands of personnel and equipment in its southern regions. Those drills, called Kavkaz 2016, include naval and land units based on Crimea, the Black Sea peninsula Moscow illegally annexed from Ukraine in 2014.
Both Moscow and Washington issued conflicting accounts of the air incident, with details differing slightly between the two accounts.
Russian Defense Ministry spokesman Major General Igor Konashenkov said two U.S. P-8 Poseidon spy planes were involved and the Sukhoi Su-27 jets were scrambled from the Belbek air base on the Crimean Peninsula to respond.
He said in a post on the ministry's Facebook page that the planes were flying near Russia's Black Sea maritime borders with their transponders turned off.
He also said the U.S. planes sharply changed their course and flew away from the Russian maritime border each time the Russian jets approached them for visual identification.
"Russian pilots acted in strict accordance with international rules of conduct for air flights," Konenshenkov said in the statement.
Pentagon spokesman Captain Jeff Davis said there were four intercepts in all, and during one, a Russian pilot flew within 3 meters of one of the U.S. planes.
He said the U.S. planes were flying what he said was routine operations in international airspace.
Russian jets have occasionally flown close to other U.S. aircraft and navy ships in the region. Earlier this year in the Baltic Sea, Russian jets buzzed the USS Donald Cook, coming within 10 meters of the warship.
