Fiji, Ireland, France and Samoa topped their pools with 100 percent records at the returning Hong Kong Sevens on Saturday while eleven-times champions New Zealand crashed out of cup contention at the first hurdle.

Meanwhile hosts Hong Kong saved the best for last as far as group action is concerned. They took a shock early lead in their final Pool A game against surprise package Samoa, with Seb Brien scoring his second try of the tournament after Steve Onosai was sent to the sin bin for the Samoans.

The Pacific Island side, who took the scalps of Australia and New Zealand in their first two games, were quick to hit back with a brace of tries from Vaa Apelu Maliko to take a 12-5 lead, only for a superb Max Denmark effort to bring Hong Kong back to within two points at half time.

The Samoans went over again through Onosai and Maliko before Hong Kong veteran Yiu Kam-shing crossed for his second try of the day, delighting the Hong Kong Stadium crowd. Samoa grabbed one last try late on as they secured top spot in the group ahead of world series champions Australia.

Brien said he scoring two tries was sweet, but his side are looking for more on Sunday.

"When you're a little kid and coming to the Sevens to watch, the idea of scoring a try against the All Blacks at the South Stand with all my family and friends in it, there's literally no better feeling in the world," he said. "But the one thing we want more than that is to get that win for the home crowd, so that's what we'll be chasing tomorrow."

The Australians beat old rivals New Zealand 24-17 in the day's final game, meaning world rugby's traditional powerhouse side will fight for ninth place at best on Sunday.

Hong Kong will face Canada on Sunday morning in the knockout tournament. New Zealand open Sunday's action against Kenya.

Samoa next face Argentina in the cup quarter finals.

Coach Ben Gollings questioned Fiji's defending in their earlier 35-21 win over Spain, but had no cause for concern in a straightforward 24-0 victory over the United States. They top Pool C ahead of the Americans and take on South Africa in their quest for a sixth consecutive Hong Kong Sevens title.

Ireland won Pool D after edging past Argentina 21-17 in their final group game, setting up a quarter-final against Australia.

It was a day of shocks in a highly competitive Group B. Great Britain recovered from a Friday night thumping by France to stun South Africa 12-10, only then to concede a converted try in the closing seconds against Uruguay, going down 19-17.

France came from behind to beat South Africa 19-17 to secure top spot and a quarter-final game against the US on Sunday.

Spain face Uruguay and Great Britain take on Japan after finishing in the bottom half of their respective groups.