UPDATE 6-Angola ruling party set for big win in disputed poll

(Adds latest results, paragraph 12)

By Paul Simao

LUANDA, Sept 7 (Reuters) - The leader of Angola's largest opposition party said on Sunday he was contesting the results of the country's parliamentary election, which showed the ruling party headed for a landslide victory.

The dispute over the poll, the first to be held in 16 years, threatens to shatter the fragile political stability that has existed since the end of Angola's civil war in 2002 and could dent the oil-rich nation's standing among foreign investors.

The international community has been watching the vote closely after tarnished elections in Zimbabwe and Kenya, hoping that the former Portuguese colony would defy its own history and emerge from the election with political consensus.

UNITA leader Isaias Samakuva, however, said the two-day vote had been badly flawed, with polling stations opening late or not at all and officials failing to properly confirm the identify of voters on registration lists. He vowed to contest the results.

"The facts suggest that the final results of this election might not rigorously reflect the wishes expressed in the ballot box by the Angolan people," Samakuva told a news conference at his party's office in the capital Luanda.

When asked if he was challenging the validity of the poll, Samakuva said: "That's right." UNITA (National Union for the Total Independence of Angola) has demanded a re-vote and vowed to take its battle to the Constitutional Court.

International monitors appear split over whether to give the Angolan election a quick and clean bill of health.