(Updates at end of first day)
* Rugby returns to Olympics with women's sevens
* Australia, New Zealand in ominous form
* Canada, Britain, France also into last eight
By Nick Mulvenney
RIO DE JANEIRO, Aug 6 (Reuters) - Rugby returned to the Olympics after a gap of 92 years in brilliant Rio sunshine on Saturday with New Zealand and Australia dominating the first day's play in the women's sevens tournament.
World series champions Australia closed out the day with an impressive 36-0 defeat of a physical Fiji side to top Pool A, while New Zealand showed ominous form in Pool B with a 52-0 thumping of Kenya and a 31-5 victory over Spain.
There were some nerves and tries aplenty on day one as Canada, France and Britain all also won both of their matches to secure spots in Sunday's quarter-finals.
The French earlier also claimed a small footnote in the history books when they beat Spain 24-7 in the first Olympic rugby action since the United States won gold in the men's 15-aside game at the 1924 Paris Games.
"We have tried to work on keeping our concentration and not getting overcome by the size of the event," captain Fanny Horta said after the French finished their day with a 40-7 rout of Kenya in Pool B.
Third seeds Canada were also in impressive form, keeping both Japan and Brazil scoreless in 45-0 and 38-0 victories that put them on top of Pool C, pending Sunday's clash with Britain.
New Zealand's try-scoring phenomenon Portia Woodman scored four tries on the opening day but was matched by team mate Kayla McAlister, who was celebrating her 28th birthday, Canada's Bianca Farella and Australia's Charlotte Caslick.
"We've been trying to treat it as just another tournament. Obviously it's 20 million times bigger, but in our heads, we're just trying to keep it relaxed," Caslick said after Australia's opening 53-0 hammering of Colombia.
The United States also thrashed the Colombians 48-0 in their second match after suffering the one upset of the day when they were beaten 12-7 by Fiji, putting in jeopardy their place in the last eight ahead of their final pool match against Australia.
The lopsided scores in some of the matches may have detracted from the experience for a boisterous crowd which at best half-filled the 15,000-seater Deodoro Stadium but World Rugby chief executive Brett Gosper was happy.
"Everything is working very well, the players have turned up and are playing a great brand of rugby," he told reporters in the stands.
"We've had good atmosphere, I think we've made a good start, really happy with it." (Editing by Ed Osmond)