Russia says one of its fighter jets intercepted a U.S. bomber flying near its border over the Baltic Sea, while Russian news reports say another Russian warplane intercepted a patrol plane from NATO member Norway over the Barents Sea.
The incidents on June 6 came a day after Montenegro formally joined NATO, becoming its 29th member in a move that produced an angry reaction from Russia.
Russia's Defense Ministry said in a statement that a Su-27 was dispatched to the Baltic Sea in the morning of June 6 after Russian radar detected an aircraft flying along the border over the international waters.
The ministry said the Russian aircraft identified the U.S. plane as a B-52 strategic bomber and escorted it until it set course away from the Russian border.
Later on June 6, Russian news agencies quoted the Defense Ministry as saying that it sent a MiG-31 jet fighter to intercept a Norwegian patrol plane flying along Russia's border over the Barents Sea.
The ministry said it had identified the Norwegian plane as an antisubmarine P-3 Orion aircraft and said it had switched off its transponder during the flight, the agencies reported.
After the Norwegian aircraft changed flight course and flew away from the border, the Russian MiG-31 fighter-interceptor returned to the base, Interfax quoted the ministry as saying.
Relations between Moscow and the West have sunk to lows unseen since the Cold War amid rancor over Russia's seizure of Ukraine's Crimean Peninsula in 2014, its backing of separatists in eastern Ukraine, and other issues.
NATO and the United States have repeatedly criticized Russia over what they have called dangerous actions by its warplanes in recent months and years.
In May, the U.S. military said its jets intercepted two Russian Tu-95 nuclear-capable bombers accompanied by two fighters that flew near the Alaskan coast.
And in September, a Russian fighter jet flew close to a U.S. Navy surveillance aircraft, in what American officials called an unsafe intercept over the Black Sea.