Image copyright AFP Image caption Voters names are checked in Kokopo in East New Britain province

Police have fired warning shots to subdue angry voters amid a chaotic start to Papua New Guinea's sprawling, two-week general election.

The shots were fired in the Southern Highlands, where there has been poll violence in the past, as frustrated voters waited for ballot boxes.

The country faces huge challenges, with more than a third of polling stations accessible only by air.

It also has two bitter rivals who have both claimed to be prime minister.

Last year the Supreme Court ruled that Peter O'Neill's election by fellow MPs was illegal and that Sir Michael Somare should be reinstated.

Papua New Guinea election PNG's eighth election since independence from Australia in 1975

The national elections, which start on Saturday, will take place over two weeks

Contested by 46 parties with 3,435 candidates to fill 109 parliamentary seats

135 women candidates

Sir Michael Somare, 76, and Peter O'Neill, 47, standing for office

Previous polls in 2002 were marred by deaths and ballot thefts, but 2007 polls were relatively peaceful

Australia and New Zealand helping oversee election logistics PNG's rival prime ministers

Both men claim to be the rightful leader and are contesting seats again.

Some 3,500 candidates are contesting just over 100 parliamentary seats.

Australia on Sunday welcomed the start of the elections.

"It's very good news that these elections are happening on time," said Richard Marles, Australia's parliamentary secretary for Pacific Island affairs.

He said the logistical difficulties meant the initial reports from polling stations were mixed.

But he added: "I think we're very pleased to see them going ahead, it's been a difficult period in PNG politics for the last 12 months. Not everything about this election is going to be perfect."

The BBC's Phil Mercer in Sydney says a small team of Commonwealth officials has been deployed to monitor the elections, but its task is enormous in such a vast, rugged country.

He says this has been a tumultuous year in the resource-rich Melanesian nation of 6.3m, with the country having two prime ministers, two police commissioners and two heads of the armed forces serving at the same time.