Police in Georgia say an explosion has ripped the front door off a television production company building during a live show critical of the president.

Nobody was injured in the explosion at Maestro television Monday morning. Rights activists called it an attack on free speech.

It came amid persistent political turmoil in the former Soviet republic, where opposition forces have protested for weeks demanding the resignation of President Mikhail Saakashvili.

The TV station was airing a live talk show usually hosted by the brother of an opposition leader who challenged Saakashvili in last year's presidential election.

Footage showed a stand-in host wincing at the sound of an explosion before a female producer hurried in screaming.