TRIPOLI (Reuters) - Muammar Gaddafi's former prime minister went on trial on Monday charged with corruption and ordering mass rapes during the war that toppled the Libyan dictator.

Al Baghdadi al-Mahmoudi could face life in jail or execution if convicted. He served as the ousted Libyan leader's prime minister from 2006 until he fled to neighboring Tunisia in August last year around the time rebel fighters took Tripoli.

The country's new leaders have been keen to try top figures from the Gaddafi era inside Libya as a matter of national pride and to show state institutions are up to the job.

But human rights groups have questioned whether such officials can get a fair trial in a country where bitterness over Gaddafi's rule still runs deep and the militia groups that helped unseat him have influence.

Under heavy security, Mahmoudi appeared in the dock looking healthy and dressed in traditional Libyan clothing.

The judge postponed the hearing to December 10 to give the prosecution and defense more time to review documents.

Tunisia extradited Mahmoudi in June, making him the first senior Gaddafi official to be returned for trial under Libya's transitional leadership.

Mahmoudi's lawyer, Mabrouk Khorchid, said in September he had not been allowed to see his client for long periods. He added he had heard the former premier had been held in solitary confinement and had suffered a nervous breakdown after Tunisia's justice minister told him an extradition was imminent.

In September, former spy chief Abdullah al-Senussi became the second former Gaddafi official to be extradited to Libya, after being captured in Mauritania holding a false passport.

A Libyan judge suspended the trial of senior Gaddafi-era intelligence official Buzeid Dorda in September after his defence lawyer said the proceedings were unconstitutional.

Dorda was arrested in Tripoli, and faced charges of killing civilians, providing weapons to kill civilians and conspiring to provoke civil war.

(Reporting By Hadeel Al-Shalchi; Editing by Andrew Heavens)