Australians were voting in national elections Saturday with conservative leader Malcolm Turnbull the slight favourite ahead of Labor's Bill Shorten, culminating a marathon race where economic management has become a key issue in the wake of the Brexit vote.

Polling stations opened at 8:00 am (2200 GMT) with some 15.6 million electors taking part in a mandatory ballot across the huge country, with a final survey putting Turnbull, a multi-millionaire former banker, marginally ahead.

After eight weeks on the hustings, a Newspoll of 4,135 people published in The Australian showed his Liberal/National coalition 50.5 to 49.5 percent in front on a two-party basis, while a poll in the Sydney Morning Herald had them in a dead heat.

Shorten's Labor needs to pick up an estimated 19 seats in the 150-seat parliament to secure the 76 it needs to govern in its own right.

The coalition, which headed into the election with a comfortable majority, can afford to lose as many as 13 seats and still hold power and has the backing of the nation's powerful media, which has cited the need for stability.

But polls are also forecasting large numbers of people planning to vote for the Greens or other minor parties and independents, which raises the prospect of a hung parliament where no side commands a lower house majority.

Turnbull, 61, is looking to bolster his power after ousting fellow Liberal Tony Abbott in a party coup last September while ex-union chief Shorten aims to return Labor to office after Labor was thumped by the conservatives at the last election in 2013.

- Unexpected headwinds -
"I feel outstanding, I've loved every minute of talking about our positive plans for Australia," an upbeat Shorten, 49, said in Sydney in a last-ditch bid to rally undecided voters to his platform of better health, jobs and education.

"What will decide this election is what is in the best interests for working and middle class Australia."

Turnbull has campaigned on his tough asylum-seeker policies, a plan to hold a plebiscite on gay marriage, and his economic credentials as the country transitions from a mining investment boom to one that is more diverse and creates new jobs.

He has also been channelling the instability sparked by Britain's shock vote to leave the European Union, warning Australia must be resilient in the face of "unexpected headwinds perhaps, like Brexit".

"We need to have the plan, we need to have the plan that meets the nature of our times, a time of opportunity and of challenge," he said.

Turnbull called an election early because crossbenchers -- politicians who are independent or from minor parties -- hold the balance of power in the upper house Senate.

They have failed to pass deadlocked legislation to overhaul unions which provided the trigger for a double dissolution of parliament, where all seats in the upper and lower houses are contested.

But some experts are suggesting the upper house could end up with more crossbenchers after the election than before, as voters fed-up with traditional politicians look for alternatives.

Dozens of minor parties and niche candidates are standing with polls suggesting they will attract significant support.

Most polls close at 6:00 pm (0800 GMT) Sydney time with the remainder two hours later due to time differences, with the elections deciding the make-up of the lower house and the 76-seat upper house Senate.

Despite the logistical difficulties in such a large country, Australians overwhelmingly abide by their obligation to vote, turnout never falling below 90 percent since it was made compulsory in 1924.