Key Points:

In the Labour strongholds of Auckland and Wellington Central, the National candidates - Nikki Kaye and Stephen Franks - are ahead of Labour's Judith Tizard and Grant Robertson, with almost 5 per cent of the vote counted.

In the other main centre, Christchurch Central, Labour's Brendon Burns is ahead but by the slimmest of margins, with 3 per cent of the vote counted there.

National remains quite convincingly ahead overall with more than 48 per cent to Labour's 31 per cent.

However it is too early to draw meaningful conclusions from the numbers as National traditionally goes out to an early lead.

With 6 per cent of the vote counted, results are showing a good surge for New Zealand First. They are just below the five per cent margin, crucial to getting a minor party into Parliament under MMP.

Of the other minor parties the Greens have 6 per cent.

The Maori Party appear to be making inroads in the Maori electorates, although Labour are holding off big challenges in Hauraki and Ikaroa-Rawhiti.

The Maori Party are ahead in five of the seven seats.

Currently, the Minister of Maori Affairs Parekura Horomia is holding off a strong challenge from his Maori Party rival Derek Fox in Ikaroa-Rawhiti. With around ten per cent of the vote counted, he is ahead by just 112 votes.

Nanaia Mahuta has a slim lead in Ikaroa-Rawhiti over Labour's Angeline Greensill.

But in all seven seats the margins are close.

National Party President Judy Kirk is one of a handful of supporters at the party's Sky City Convention Centre at this stage.

She says she is cautiously confident, but has warned against reading too much into the early results.

"It depends what booths come in first - we know from last time we had some of our strongest booths coming in first and you have to be careful not to get too carried away until you see the bigger picture," she said.

Labour's Phil Goff says it is too early to read anything into the results as rural seats always come through first and favour National.

Labour leader Helen Clark is bidding to win a record fourth term, while National's John Key is seeking to return his party to power.

Other crucial issues which will unfold durign the night are the fate of New Zealand First and the Greens as well as the other minor parties.

Turnout is tipped to be high thanks to good weather nationwide and strong advanced voting.