Libya's election commission said on Wednesday that Saif al-Islam Gaddafi, the son of the former ruler and a major candidate in December's planned presidential election, was ineligible to run, compounding the turmoil surrounding the vote.

Gaddafi was one of 25 candidates the commission disqualified in an initial decision pending an appeals process that will ultimately be decided by the judiciary. Some 98 Libyans registered as candidates.

Disputes over the election rules, including the legal basis of the vote and who should be eligible to stand, threaten to derail an internationally backed peace process aimed at ending a decade of violent factional chaos.

The commission said Gaddafi was ineligible because he had been convicted of a crime. A Tripoli court sentenced him to death in absentia in 2015 for war crimes committed during the uprising against his late father Muammar Gaddafi in 2011.

He appeared in that trial by video-link from the town of Zintan, where he was being held by fighters who captured him as he tried to escape Libya after his father's overthrow. He has denied wrongdoing.

Two other well-known candidates, former premier Ali Zeidan and former parliament Nouri Abusahmain, were also excluded.

(With input from agencies)