CNN  — 

New photos released by Belgium give a close-up look at some interesting Russian aircraft that Belgian F-16 fighters encountered during a four-month stint as part of NATO’s Baltic Air Policing mission.

The Russian planes intercepted by the Belgians included a Su-27 Flanker, a Tu-134AK, an Il-76, an An-72 and an An-12PPS, according to The Aviationist blog, which reported on the photos last week. The photos were also posted on the Facebook page of the Begium Air Component unit, the 1st Squadron Stingers.

Four Belgian F-16s were based out of Amari Air Base in Estonia, a NATO member country, from January to April. The Belgian jets paired with Spanish Eurofighter Typhoon jets based out of Siauliai, Lithuania, to keep watch over the airspace of Estonia, Lithuania and Latvia, all of which joined the alliance in 2004.

Baltic airspace has seen an increase in Russian air activity in recent years as tensions between Russia and NATO escalated after the Russian takeover of Crimea from Ukraine in 2014.

In April, the U.S. accused a Russian Su-27 jet of doing a barrel roll over a U.S. Air Force RC-135 reconnaissance plane over the Baltic Sea. The Russian fighter came within 50 feet of the U.S. jet during the maneuver, a spokesman for the U.S. European Command said.

Russia denied its aircraft performed any dangerous maneuvers as it intercepted the U.S. plane.