Serena Williams and Venus Williams have progressed to the second round of the women's doubles event at the Australian Open, courtesy of a straight-sets victory over Stefanie Voegele and Camila Giorgi.

The American pair, who are seeded 12th, took the opening set with single break of serve.

With temperatures on Show Court Two reaching 40 degrees Celsius, there was a brief delay midway through the second set as the heat caused a fan to pass out in the stands.

Serena and Venus remained cool, however, and won 29 out of 43 second-set points to seal a 6-3 6-1 victory inside 70 minutes.

Vera Dushevina and Olga Govortsova will provide the opposition for the sisters in round two.