Sonny Bill Williams marked his debut with a try as New Zealand won all three of their group matches ©World Rugby

Hosts New Zealand fought back from 7-0 down to beat South Africa and maintain their 100 per cent record at the third World Rugby Sevens Series event of the season in Wellington.

The Kiwis were one of three teams to seal a hat-trick of wins along with defending overall champions Fiji and Australia.

Boosted by the inclusion of World Cup XVs winner Sonny Bill Williams, who marked his debut by scoring a try with his first touch, New Zealand made light work of Russia in their opener as they ran in six tries in a thumping 38-7 success.

The home side then went on to prove too strong for Scotland as they claimed a comfortable 27-7 victory before they met the Blitzboks, who had also beaten both Russia and the Scots.

South Africa looked keen on upsetting the odds and raced into an early advantage in the eagerly-anticipated Pool A clash as Kwagga Smith’s converted try gave them a 7-0 lead.

Sam Dickson went over just before half-time to cut the deficit to two and Akira Ioane managed to turn the contest on its head shortly after the break to put New Zealand 10-7 in front.

His effort was converted to add another two points to their total but the topsy-turvy nature of the contest continued when Cheslin Kolbe’s converted try saw South Africa regain the advantage.

As the match entered the dying stages, Joe Webber popped up with a vital try, which was then converted, to hand New Zealand a dramatic 19-14 win to seal top spot in the pool.

Fiji were also in good form on the opening day as they progressed to the last eight with their unbeaten record in tact
Fiji were also in good form on the opening day as they progressed to the last eight with their unbeaten record in tact ©World Rugby

They will go on to face Kenya in the quarter-finals tomorrow after the African side finished second behind Australia, who also picked up wins over Canada and Portugal, in Pool D.

“Hopefully I can grow into the tournament and just keep learning,” Williams said.

“It was a sneaky scab try, I was just backing up, but like I said I just want to learn.

"I am grateful to be playing amongst such talented players.

“It is always good to play at home, and in the All Blacks jersey, in Wellington, from a New Zealand perspective I'm not sure it gets much bigger than this.”

Current overall leaders Fiji, who won the opening event of the campaign in Dubai, ran in a total of 17 tries as they secured victories over Argentina, Wales and Japan to finish top of Pool B.

The United States lie in wait for the Fijians in the quarter-finals after they were second in Pool C behind England, who topped the group despite a 17-14 reverse at the hands of Samoa.

England will go up against Argentina in the last eight while South Africa will face Australia in the pick of the quarter-finals tomorrow.