From the Wikipedia page 
The Abrene County (Latvian: Abrenes apriņķis) was an administrative district in the Republic of Latvia with an area of 4292 square kilometers, formed in 1925 from the northern part of the Ludza district and the western part of the Ostrov region as the Jaunlatgale (New Latgale) district, but this was renamed Abrene in 1938. The district included the towns of Balvi and Abrene and 14 villages, and the civil parishes (Latvian: pagasti) comprising the district were reorganized thrice (there were 12 in 1929, 13 in 1935, and 15 in 1940). 6 eastern civil parishes – Purvmalas (Bakovo), Linavas (Linovo), Kacēnu (Kachanovo), Upmalas (Upmala), Gauru (Gavry) and Augšpils (Vyshgorodok), as well as the town of Abrene (a total area of 1293.6 square kilometers with 35,524 inhabitants) – were annexed to the Russian Soviet Federative Socialist Republic in 1945. This part of the former Abrene district is now part of Russia as the Pytalovsky District of Pskov Oblast, bordering Latvia. "Abrene region" in current usage very often treats the area joined to Russia as though it had comprised the entire district, which can be misleading; nearly three-quarters of the former district are in Latvia, but many treatments of the transfer of the eastern pagasti cite interbellum demographic statistics for the whole of the region, rather than by civil parish.