Georgian President Mikheil Saakashvili casts his ballot in a parliamentary election seen as the first big challenge to his power after nearly a decade in office.

Tensions are high here after a prison abuse scandal emerged just weeks ago.

This is just some of video footage which purports to show prisoners being beaten and raped in a Tbilisi jail.

Pro-Western Saakashvili must step down vote next year, but constitutional changes will move the seat of power from president to prime minister.

So Saakashvili could become prime minister if he wins this poll.

He needs to head off a challenge led by this man, tycoon Bidzina Ivanishvili, whose Georgian Dream Movement could emerge with a majority over Saakashvili's United National Movement.

Ivanishvili accompanied his wife to the polling station to cast her ballot, but he refused to vote himself after the Georgian government stripped him of his citizenship last year.

He said this could be the first time in Georgian history that the government is changed through elections.

The grim video footage of the abused prison inmates has bolstered Ivanishvili's campaign, as his party makes the case that Saakashvili has become an undemocratic leader.

Summer opinion polling showed many voters remained undecided, but there have been no polls since the abuse scandal emerged.