Russia challenges US after Baltic jet face-off
Russia says it was right to confront a US Air Force reconnaissance plane over the Baltic Sea on Friday.
The Pentagon said a Russian jet fighter acted in an "unsafe and unprofessional manner", and performed a barrel roll over its plane.
Russia said that the American jet had turned off its transponder signal, which helps others identify it.
It is the second incident in the Baltic this month in which the US has accused Russian planes of flying aggressively.
"All flights of Russian planes are conducted in accordance with international regulations on the use of airspace," a statement by the Russian defence ministry said. "The US Air Force has two solutions: either not to fly near our borders or to turn the transponder on for identification."
US jets "regularly" try to approach Russia's borders with transponders switched off, the statement said. Over the past 18 months, Russia has been repeatedly accused of the same practice over the Baltic and near UK waters.
It is not clear how close to Russia's waters Friday's incident occurred.
On Friday, Pentagon spokesman Daniel Hernandez said there had been "repeated incidents over the last year where Russian military aircraft have come close enough to other air and sea traffic to raise serious safety concerns".
"The US aircraft was operating in international airspace and at no time crossed into Russian territory," he said.
"This unsafe and unprofessional air intercept has the potential to cause serious harm and injury to all air crews involved."
Such actions could "unnecessarily escalate tensions between countries," he said.
Mr Hernandez said the Su-27's "erratic and aggressive manoeuvres" also threatened the safety of the US aircrew, coming within 7.6m (25ft) of the fuselage of the American plane before conducting its barrel roll.
Military encounters between Russia and the US and its allies have escalated significantly over the past two years, ever since Russia's annexation of Crimea and the breakdown of relations between East and West.
Two Russian planes flew close to a US guided missile destroyer almost a dozen times in the Baltic on 13 April.
The BBC's Gary O'Donoghue in Washington reported after the destroyer incident that Russia's actions were regarded by defence analysts as a flexing of muscle, a reminder that Russia has military might and cannot be pushed around.