A hat-trick to sevens rookie Frank Halai muscled New Zealand to a 34-7 win over Argentina on the first day of the sevens rugby tournament in Wellington yesterday.

New Zealand captain DJ Forbes had earlier said his team had to get through three finals on day one, and they managed that in style with comprehensive wins over Scotland and Papua New Guinea earlier in the day.

But it was the final match of the night that saw the New Zealanders really cut loose, running in five tries with an impressive display of power and precision.

Halai and another emerging talent, Declan O'Donnell, featured in the two opening tries, the first coming to Halai barely 40 seconds into the match.

O'Donnell secured the second soon after, then Tim Mikkelson crossed to give New Zealand a 19-0 halftime lead.

That was extended early in the second spell, Halai picking up his next try just 30 seconds after kickoff, then adding the third two minutes later.

The New Zealanders dominated possession and controlled the match from then on, the only hiccup coming as fulltime neared and Diego Palma touched down for Argentina's only try with just over a minute remaining.

After a scrappy, disjointed effort to down Scotland 29-12 in their opening match, the hosts put in a more accomplished display to overwhelm Papua New Guinea 45-0.

Coach Gordon Tietjens has a history of unearthing stars at this tournament and in the hot-stepping Buxton Popoalii he may have added another to that list.

He jinked his way through Scotland's defence seconds after entering the fray and then again showcased his sidestep in crossing for two tries against Papua New Guinea.

New Zealand, who have not won the tournament since 2008, started slowly against Scotland, but emerged with the win, scoring five tries to two.

Playmaker Tomasi Cama and Halai crossed in the first half, before O'Donnell stepped past two defenders to extend their lead after the resumption.

Halai added his second before Popoalii crossed late on.

But Scotland managed to expose some defensive shortcomings in the inexperienced New Zealand lineup to grab second-half tries to Andrew Skeen and Michael Fedo.

The Shane Howarth-coached Papua New Guinea posed no such problems and New Zealand enjoyed a seven-try romp with David Raikuna, DJ Forbes, Solomon King, Scott Curry and Toby Arnold adding to Popoalii's brace.

Elsewhere, South Africa's Renfred Dazel was left with egg on his face after his blunder allowed France to cause the biggest upset of the day.

With the fancied South Africa leading 12-7, Dazel seemed destined to score a try but stepped out of bounds in the in-goal area. With time up on the clock, France's Renaud Delmas scooted through to dot down under the posts to give them an unlikely 14-12 win. Australia sounded a warning with a disciplined 29-5 win over last year's Wellington sevens runners-up Samoa.