World champions Wales, shock victors in Dubai four years ago, ran out 33-5 winners over Uruguay, but England were handed a fright against Portugal before two late tries saw them beat Portugal 21-7, Pool F rivals Argentina thumping Hong Kong 47-7.
There was no dream start for hosts Russia, who were comprehensively outplayed 31-0 by a sharp-looking South Africa team for whom Seabelo Senatla, fresh from the under-20 world championships in France, scored an outstanding double.
The All Blacks ran in four tries through Sherwin Stowers (2), Gillies Kaka and Kurt Baker in beating Canada 31-12 in sweltering conditions that saw temperatures rise to 33 degrees Celsius (91F) with high humidity.
The Canadians hit back with two second-half tries from Nanyak Dala and Harry Jones, but the All Blacks were halfway to the ice baths by then.
For New Zealand captain DJ Forbes, returning from a long injury lay-off, it was merely a question of getting the job done, with the remaining pool matches to be played on Saturday and finals on Sunday.
“It’s definitely good to be back in the team and especially at the World Cup,” said Forbes.
“That said, we’re a little disappointed with the tries we let through, but it’s the World Cup and teams are going to take it up a notch.”
Forbes said that the sevens team’s lack of success at the World Cup, their last victory coming 12 years ago in the Argentinian resort of Mar del Plata, mirrored that of the senior 15-a-side team, who claimed the title at the 2011 World Cup they hosted after a gap of 24 years.
“It’s a little bit similar to the All Blacks: we’ve dominated world series rugby but haven’t had our hands on the World Cup as much as would have liked to.”
The weekend, Forbes said, would be won by “doing the little things well, and making as few mistakes as possible”, with Pool D rivals the United States beating Georgia 26-19.
There was a hint of a surprise in the opening match of the day when Zimbabwe led Samoa 14-7 at half-time thanks to tries from Daniel Hondo and Gardener Nechironga.
But the South Sea Islanders, consistent performers on the sevens circuit, hit back to win 21-14, Kenya running out comfortable 45-5 winners over debutants the Philippines in the other Pool C match.
“We stuck to our task there, the Philippines side made it difficult for us for the first three or four minutes,” said Kenya coach Mike Friday.
“First and foremost we’re happy to get the win, everyone got on the park, but we know points difference is all-important here.”
Perennial favourites Fiji hammered neighbours Tonga 45-0, while Wales always had too much power for Uruguay in the second Pool E match, winning 33-5, with one try to James Davies, brother of British and Irish Lions centre Jonathan.
“It is a one-off tournament but the thing is with the pool, every little thing matters because you aren’t guaranteed to go through if you finish top two,” said Wales coach Paul John.
“If a decision goes against you, or you miss a conversion, points difference is huge. That is the nature of a 24-team tournament.”
Hard-hitting Australia will go into day two atop Pool A after beating Spain 21-0, while a Julien Candelon-inspired France overcame Tunisia in a niggly match, 24-7.