Su-30 Intercept

Su-30SM “81 Blue” with tail number RF-81885. (Spanish Air Force pic)

The Russians regularly fly over the Baltic in International Airspace and NATO dispatches jet fighters to follow them around. This photo is from one such encounter. I suspect that the Russians make these flights as a matter of 'freedom of navigation'. It's like if you don't exercise your rights, you are liable to lose them. Also flying (or sailing) over the Baltic is the only way to get from mother Russia to Kaliningrad. Both sides get to exercise their pilots and aircraft which is essential if you are going to bother about having jet fighter aircraft in the first place.

Excerpt from Defence Blog:

The interception was carried out by F-18M aircraft from Spain’s Wing 15, currently deployed to Šiauliai Air Base in northern Lithuania under the Vilkas detachment. . . . The intercepted aircraft included Russian Su-30SM multirole fighters armed with air-to-air missiles and cluster munitions. . . . markings visible on the tail show the aircraft belongs to the Naval Aviation branch of the Russian Navy.