No Asian side has ever secured a podium finish in the 39-year history of the showpiece women's event, but Japan made a superb start in seeking to end that blank.

Two points in the fifth end and a steal of two more in the sixth propelled Satsuki Fujisawa's side to a 7-5 triumph over Finland in their morning clash.

They then dominated their afternoon encounter with Italy, sealing a 10-3 win in the eighth end.

Last year's bronze medallists Russia played the same two opponents today, and proved similarly successful.

They first beat Italy 8-2 before a superb display by skip Anna Sidorova inspired a 7-4 victory over Finland.

Two-time defending champions Switzerland only played once on the opening day of round-robin action.

But the team, skippered by 2014 gold medallist Binia Feltscher, won a tough encounter with an experienced United States side, 5-4.

“It's super-cool to be back at the World Championships and it's super-cool to be back in Canada again," said Feltscher.

"The whole team was playing well and it was a close game with a good ending.

"We're looking to be in the first half of the field.”

Hosts Canada, seeking to reverse a run of successive final defeats to Switzerland, also made a winning start in beating Denmark 6-4.

Germany and Sweden are the two other unbeaten teams, respectively beating South Korea 8-5 and Scotland 5-3.