Russia's Federal Security Service says it has broken up a ring that was smuggling firearms into the country from Latvia.

The service, known by its initials FSB, said in a statement Thursday that more than 30 weapons were seized in a raid in the Pskov region, which borders Latvia and Estonia. The weapons included submachine guns and carbines, the statement said.

The FSB says one Latvian citizen and eight Russians were arrested in the case.

The arrests come amid heightened tension between Latvia and Russia. Latvia and its former Soviet Baltic neighbors are unsettled by Russia's annexation of Crimea and alleged supply of arms and troops to separatist rebels in Ukraine's east. Russia in turn criticizes Latviafor language laws it claims effectively ban the use of Russian.