HELSINKI (AP) — An Estonian court has decided to release on parole a former security official who was found guilty of treason for passing on top NATO secrets to Russia in a case widely considered to be one of the worst spy scandals within the military bloc.

The Tartu County Court said Thursday that Herman Simm, who was sentenced to 12-1/2 years in prison in 2009, is eligible for parole without electronic surveillance.

The 72-year-old Simm, who is a former head of security at the Estonian Defense Ministry, was found to have passed over 2,000 pages of NATO and other diplomatic information to Russia's foreign intelligence service SVR between 1995 and 2008.

In retaliation, two Russian diplomats had their accreditation to NATO's Brussels headquarters cancelled in 2009.

Estonia has been a NATO member since 2004.