The 71-year-old who has not been named "betrayed state secrets at the expense of Austria for a foreign secret service", a Salzburg court ruled.

He also "deliberately disclosed a military secret", according to the verdict.

The court case began in March behind closed doors to avoid revealing classified military information.

He was charged with betraying state secrets over a period of more than 25 years, for which he received roughly 280,000 euros ($310,000).

His defence lawyer said his client had been paid 220,00 euros for information which was available from open sources.

Prosecutors said the information the defendant passed related primarily to Austria's weapons systems and the organisation of its land and air combat forces.

They say he maintained contact with Russian intelligence into his retirement.

At the time of his arrest Austrian media described him as a mid-ranking officer who worked in the defence ministry's planning department.