The Latvian military reported Friday that it has observed a Russian submarine support ship just 18 nautical miles (33 km) from its territory. While the sighting may not be unusual given the country’s relative proximity to the Russian region and naval base of Kaliningrad, it does raise fresh concerns about submarine activity in the Baltic region.

The sighting, believed to be of a Kashtan-class submarine support ship, comes just one week after Sweden launched its largest submarine search since the end of the Cold War after people reported seeing something off the coast of the Stockholm archipelago -- across the Baltic from Latvia. That was quickly followed by reports from Norwegian scientists that they had spotted a partially surfaced Russian submarine near the Arctic Circle




Tension in the Baltic Sea is rising, with Russian aircraft and possibly naval vessels engaging in more forays over international waters close to other nations' airspaces. Russia had simulated an air attack on Sweden in 2013. 

Despite the search, Sweden was unable to find the purported Russian submarine. But increased Russian military aircraft activity this week has put NATO and other European countries on high alert as Russia seeks to showcase its military strength and possibly increase its influence in the region.