SWEDEN’S top military commander says Russian fighter pilots are behaving in an increasingly aggressive manner in northern Europe, flying dangerously close to Swedish air force jets and in some cases even releasing flares at them.

Supreme Commander Sverker Goransson told a seminar on the Swedish island of Gotland on Monday that the Russians are breaking the normal rules of conduct for when military aircraft meet in the air.

He said examples include Russian planes breaking formation, flying at unsafe distances and using “countermeasures” that “nearly bounce off the metal” of the Swedish aircraft.

The Swedish military on Tuesday confirmed he was talking about decoy flares designed to divert incoming missiles.

Goransson said he believes their behaviour is “sanctioned at the highest level. Otherwise they wouldn’t act this way.”

NATO is also considering how to respond to the threats posed by an increasingly “bold” and “aggressive” Russia.

The 28-member defence alliance’s naval forces met in London this week to discuss Russia’s maritime operations.

“Russian international maritime presence has grown significantly in recent years, specifically since the Ukraine crisis erupted in 2014,” senior NATO commander General Adrian Bradshaw, told the London conference.

“The Russian Federation is shadowing and presumably collecting intelligence from NATO nation naval units in the Baltic, the Atlantic, the Mediterranean and the Black Sea, using methods that can be considered bold and sometimes aggressive,” he said.

NATO will from September to November launch its largest exercises in more than two decades, in regions including the Atlantic Ocean and the Mediterranean Sea.

In a rare move, the US military released a video last month of a Russian Su-24 bomber flying past an American warship in the Black Sea, while Sweden last year launched a massive hunt for a suspected Russian submarine in the Stockholm archipelago.

Russia is upgrading its naval capabilities, and in May unveiled designs for two new major warships, a multipurpose heavy aircraft carrier called the “Shtorm” and a new class of destroyer called the “Shkval”.