Counting is under way in Papua New Guinea's sprawling elections, officials said, but voting has been marred by claims of rigging, electoral roll flaws and ballot paper shortages.

The last polling stations are due to close on Saturday after two weeks of voting for the 111-seat parliament across the vast and remote country where previous elections have been tarnished by violence.

The Pacific nation's leader, Peter O'Neill of the People's National Congress (PNC), has hailed this year's poll as "calm and peaceful", even as some voters complained that their names had vanished from the electoral roll.

'Cash allowance'

Students in the second largest city, Lae, burnt ballot papers after complaining that an insufficient amount was allocated to their university, while election officials were found carrying US$57,000 in cash, media reported.

The electoral commission later reportedly said the money was an allowance for polling staff.

Meanwhile voting in the capital, Port Moresby, was delayed for several days after polling officials went on strike over unpaid allowances.

"Polling and now counting is a success. We should be proud that this election we have managed [to] see it through," Electoral Commissioner Patilius Gamato told Thursday's Post-Courier, adding he would not declare the poll a failure.

O'Neill on Wednesday slammed opposition politicians for questioning the commission's integrity after they called for results in his Ialibu-Pangia seat not to be declared first as it could give the PNC an advantage.

"Let the electoral commission get on with its job, and in that process, these failed leaders of the past must stop trying to tarnish constitutional office holders," O'Neill said in a statement.

There is no opinion polling in PNG, so it is unclear who holds the advantage. But no party has ever won a majority, meaning a coalition is likely, held together by strategic political appointments.

O'Neill's main threat is seen as Don Polye's Triumph Heritage Empowerment Party.

Polye on Monday claimed leaders in Hela electorate had been "deliberately and openly rigging the election", calling on Gamato to declare the vote in the province as failed, the Post-Courier said.

Former New Zealand governor-general Sir Anand Satyanand, who heads the Commonwealth Observer Group monitoring the elections, said it was too early to declare any failure.

"Election officials ... have got a week to put measures in a better place than they are at the moment," he told the Australian Broadcasting Corporation on Monday.

"I would not responsibly use the word 'failed'.

"Whether it reaches a pass mark is for this week to establish."