The Swedes, skipped by double world champion Niklas Edin, were in good form as they look to back-up the crown they captured in Halifax in Canada last year.

Japan had their best moment when skip Yusuke Morozumi scored two points thanks to a double take-out in the fourth end, which levelled the contest at 3-3.

The reigning champions sealed things in the final end, however, with Edin knocking out a Japanese stone to confirm his team's success.

"It was a good start, but we had a lot of communication problems in sweeping," said Edin.

"The ice, as it is right now, is pretty tricky, but I think we got into it pretty well after half the game.

"We got a lead, and luckily we could keep that lead for the whole game.

"It was definitely not an easy win."

Action was begun by International Olympic Committee President Thomas Bach, who delivered the ceremonial first stone.

The German is a guest of honour and is helping the World Curling Federation (WCF) mark their 50th anniversary. 

Hosts Switzerland also got off to a winning start as they beat Germany 8-2 in their round-robin opener.

Elsewhere, there were comfortable opening session victories for Scotland, who beat South Korea 9-3, and Norway, who saw off Russia 11-3.

The Scots were one of four teams to play twice on opening day and are the only side to boast a 100 per cent record after a 6-3 win over Norway.

Other evening session games saw Russia recover to beat Korea 9-8, while Denmark thrashed United States 7-1.

Canada got off to a winning start by beating Finland 7-3.

The top four after the round robin stage will progress to the play-offs.