WELLINGTON (AFP) - New Zealanders were voting on Saturday in a general election to determine who will lead the country for the next three years and under strict laws allowing limited election coverage on polling day.

On the eve of the vote, both the centre-right National Party of Prime Minister John Key and the main opposition centre-left Labour Party led by David Cunliffe predicted the outcome would be close.

Voting began at 9.00am and will close at 7.00pm, with the media limited to reporting the poll is on and when results are expected - but barred from using words or images which could be seen to influence voters.

This has led to the main Saturday morning newspapers making no reference to the election at all.

However, the Electoral Commission said Friday that more than 500,000 of the 3.06 million registered voters had cast early ballots when media election coverage was in full swing.

There is heavy rain across most of the country and poor weather historically meant a low voter turnout.

First indications of the election outcome are expected within four hours of the polls closing.

There are 71 electorates, with the remaining seats filled through party votes, bringing the number of MPs in parliament to around 120 under New Zealand's complicated proportional voting system.