Bira-class refers to a decades-old design of the former cargo ships retrofitted by the Soviet navy in the 1960's for use as military landing craft.
This particular vessel was 5 nautical miles, or about 9 kilometers from Exclusive Economic Zone (EEZ) waters under Latvian jurisdiction.
Armed Forces on 21 APR in LV EEZ 5 nmi from territ. waters spotted RU Navy's support ship Bira.— NBS (@Latvijas_armija) April 21, 2015
This type of ship was also encountered in October of 2014.