Former captain Denis Urad sent a copy of the letter to opposition media in March. In it, Interior Minister Ivan Kubrakov demanded the defense minister involve the army in suppressing protests. 

State news agency BelTA reported that Urad had been convicted of treason for releasing state secrets. "Urad's action ... has caused significant harm to national interests," BelTA quoted state prosecutor Mikhail Kovalev as saying. 

Belarusians protested for months last year after a presidential election that opponents said was rigged to keep veteran leader Alexander Lukashenko in power. Lukashenko has denied electoral fraud and police have cracked down on protests, detaining thousands. The Belarus opposition said this week one of its jailed leaders, Maria Kolesnikova, could face 12 years imprisonment.