A pair of Dutch of F-35 fighter jets intercepted a formation of Russian military aircraft flying near a NATO zone of responsibility in Polish airspace, Dutch officials have revealed, US network FOX news reports.

The incident occurred on Monday, with “a currently unknown aircraft approaching the Polish NATO area of ​​responsibility from Kaliningrad,” a Russian enclave in the Baltic Sea, the Dutch defense ministry said, citing Reuters.

“After identification, it turned out to be three aircraft: one Russian IL-20M Coot-A accompanied by two Su-27 Flankers”, Dutch officials reportedly added.

“Dutch F-35s escorted the formation from a distance and delivered the escort to NATO partners.”

The Polish Ministry of Defense clarified to Politico that the aircraft were traveling over international waters and they did not enter the country’s airspace.

The incident comes as tensions between NATO and Russia run high following Moscow’s invasion of Ukraine.

As Politico reports, the United States warned on Tuesday that Russia still has a powerful air force, underscoring the need to provide further support to Ukraine as Russia’s offensive continues in the eastern Donbass region.

Security officials from more than 50 countries are meeting in Brussels to coordinate aid to Kiev, and discussed giving Ukraine more artillery, ammunition and armored forces — but mainly the strengthening of air defense amid concerns over Russian aircraft. “Although the Russian capabilities – the ground forces – are very discouraged, very, very weakened, very depleted, the Russians still have a fairly significant air force,” a senior US administration official said on condition of anonymity.