The Russian SU-27 Flanker fighter made the maneuver on Wednesday near a US Navy P-8A Poseidon aircraft that was conducting routine operations in international airspace, Pentagon spokesman Navy Capt. Jeff Davis said.

A US defense official speaking on condition of anonymity told the news agency AFP the Russian plane flew within 30 feet (9 meters) of the P-8A before closing to just 10 feet.

Moscow said the intercept was conducted "in strict accordance with international rules" because the Americans were trying to snoop on Russian army exercises.

Russian Defense Ministry Spokesman Maj. Gen. Igor Konashenkov said in a statement on Wednesday that the Poseidon aircraft did not have its transponders turned on and had approached Russia's southern border twice.

Russian jets had been deployed to intercept the aircraft and "Russian pilots acted in strict compliance with international flight rules," he said.

A senior US defense official said the Navy Poseidon had its transponder turned on during the entire flight. The official, who was not authorized to discuss the matter publicly, spoke on condition of anonymity.

According to the US, the Russian jet conducted four intercepts of the Poseidon, and the one that was considered unsafe lasted about 19 minutes.

"However, we have concerns when there is an unsafe maneuver like this," Davis said. "These actions have the potential to unnecessarily escalate tensions, and could result in a miscalculation or accident."

In a dramatic incident earlier this year, Russian jets buzzed over the USS Donald Cook in the Baltic Sea, coming within 10 meters of the warship.

Relations between Russia and the West are at their worst since the Cold War, due to Moscow's seizure of Crimea from Ukraine and alleged fueling of a separatist conflict in the former Soviet republic.

jbh/kl (AFP, AP)