Reigning champions Sweden started to defend their title by beating Italy 7-1 while Canada and Switzerland survived opening game scares at the ice hockey world championship on Saturday.

Jamal Mayers scored two goals, including the winner, as Canada escaped with a 3-2 win over Germany in a Group C clash while Switzerland rallied past Latvia 2-1 in Group A.

In another Group C meeting, Jaroslav Halak made 24 saves to record a shutout as Slovakia blanked Norway 3-0.

The only country to win both Olympic and world gold in the same year, Sweden allowed Italy to take an early 1-0 lead with a powerplay goal from Georgio de Bettin.

However, they roared back with seven unanswered goals.

Fredrik Emvall and Johan Davidsson powered the comeback with two goals each while Tony Martensson, Jonathan Hedstrom and Per Hallberg each scored once to send Sweden to the top of the Group A standings.

Germany who beat Canada 5-1 in 1996, again forced Canada to dig deep for the victory.

After the teams traded goals in the opening two periods, Mayers notched the winner with just over eight minutes to play, slamming home the puck into an open net after German goaltender Dimitri Kotschnew got caught out of position.

Slovakia, world champions in 2002, took command of their game midway through the opening period when Marek Uram and Boston Bruins' Zdeno Chara scored then rode Halak's sparkling netminding to a well-earned win over Norway.

In Moscow, Latvia struck first with a goal by Lauris Darzins to grab the early lead before the Swiss hit back with a pair of second-period goals from Sandy Jeannin and Adrian Wichser