Australian Prime Minister Malcolm Turnbull said he had "every confidence" of retaining government, despite Saturday's national elections failing to give his conservative coalition an immediate clear victory.

"Based on the advice I have from the party officials, we can have every confidence that we will form a coalition majority government," the 61-year-old told supporters early Sunday.

The multi-millionaire former banker who deposed his predecessor Tony Abbott in a Liberal Party coup in September had hoped to hold onto a clear majority of seats in parliament's 150-seat lower house.

But as he addressed an election function in Sydney after midnight, neither his ruling conservatives or the opposition Labor Party had the required 76 seats to form government.

In a defiant speech, Turnbull accused Labor of running a scare campaign about the public healthcare system and said he would seek to unite Australians.

"The election is over. Only the counting remains. And now is the time to unite in Australia's aid, in Australia's service to ensure that we can have truly the very best years for our country ahead of us," Turnbull said.

Earlier, Labor leader Bill Shorten declared to party faithful in Melbourne that his party was "back" after just three years in opposition.

Turnbull had used the chaos sparked by the recent British vote in support of leaving the European Union to call on Australians to re-elect the coalition.

The Australian leader added that he did not expect final results from the election to be known until next week given that the electoral commission will not resume counting postal votes until Tuesday.