Georgia on Friday arrested ex-president Mikheil Saakashvili, who returned from exile ahead of local elections in the Caucasus country gripped by a protracted political crisis, the prime minister said.

"Georgia's third president Mikheil Saakashvili has been arrested today and sent to jail," Prime Minister Irakli Garibashvili told a news conference.

The 53-year-old's arrest is expected to spark upheaval in Georgia, ahead of Saturday's local elections seen as a key test for the increasingly unpopular ruling party. 

Prior to his arrest Saakashvili lived in Ukraine where he headed a government agency steering reforms. 

He said Georgia's law enforcement agencies had tracked Saakashvili's movements from Ukraine to Georgia and "chosen a time and place for the police operation that would create minimal obstacles for the arrest".

Saakashvili was convicted in absentia on abuse of office charges in 2018 and sentenced to six years in prison. He denies any wrongdoing and says the case is politically motivated.

On Friday morning, he said in video messages on Facebook that he had returned to Georgia and was in the western city of Batumi.

He called on his supporters to take to the streets against the government.

Saakashvili -- who swept to power in 2004 following a peaceful uprising -- still commands a fiercely loyal following in the Caucasus country.

Critics have accused the ruling Georgian Dream party of using criminal prosecutions to punish political opponents and journalists. Interpol turned down requests from Tbilisi to issue a red notice against Saakashvili.