Bassem Khashan had been sentenced to two jail terms of three years each earlier this month.

"The court examined the two cases.... The first verdict was cancelled for lack of proof," Supreme Judicial Council spokesman Abdel Sattar Bayraqdar said in a statement.

Kashan will be retried in the second case and has been set free until a new trial is held, he said.

Over the past two years Khashan had tracked down 350 cases of corruption by local officials in the southern province of Muthana and alerted authorities, according to Majid Abu Kalal of the Dhar NGO.

His sentencing on February 7 had sparked an uproar among his supporters, both online and on the streets of Samawa, the provincial capital of Muthana, where protests were held to condemn the verdict.