Australia finished undefeated on day one of the Rugby World Cup Sevens after beating Japan 31-12 in their third Pool match in Hong Kong.

Matt Hodgson scored two tries with Australia's others coming from Josh Gamgee, Nick Reily - his fifth of the tournament, making him the leading try scorer to date - and Kieran Massey.

The big crowd gave Japan plenty of support and were delighted when Yohei Shinomiya scored two late tries for Japan to bring the final score to 31-12.

Earlier, Australia smashed hosts Hong Kong 38-5, thanks to tries from Reily, Gamgee, Andrew Brown, Shawn Mackay and Anthony Sauer, who scored a double in the second half.

The Australians will play their last two pool matches against Canada and Fiji on Saturday.

France handed England a shock defeat, ending a three-year unbeaten streak and badly denting their hopes of uniting the 15-a-side and Sevens world titles.

The 28-17 victory, in front of a stunned Hong Kong crowd, also handed the initiative to defending champions New Zealand, who survived a testing encounter with Pacific rivals Tonga.

France's Jerome Naves secured the win on a day for the underdogs, capitalising on a mistake by late substitute Rob Thirlby to sprint half the length of the field and score beneath the posts.

New Zealand trailed Tonga 7-12 at half-time before hitting back with tries from Highlanders flanker Josh Blackie and Orene Ai'i to remain on course for the first back-to-back World Cup Sevens titles.

The tense late encounters came as a surprise after both favourites had made flying starts to their campaigns. New Zealand breezed past South Korea and Ireland while England were electric against Georgia and Italy.

Brought to you by AAP © 2024 AAP