A court in Estonia has found a former military officer and his father guilty of committing treason by spying for Russia.

The Baltic News Service reports the court in Tallinn ruled Monday that 38-year-old Deniss Metsavas — an ex-major with the Estonian army — and his father, 65-year-old Pjotr Volin, sold classified information to Russia's military intelligence service, the GRU.

The news service says the court found that Metsavas passed the information for a decade and sentenced him to 15 ½ years in prison.

Volin worked with the GRU for approximately half as long and received a six-year prison term.

Estonia, a former Soviet republic, has had several high-profile cases of alleged spying since the country declared independence in 1991. Both Estonian and Russian citizens have been accused of providing sensitive information to Moscow.