The Williams sisters have advanced to the third round at the Australian Open, with top-ranked Serena fending off set points before going on a 10-game roll to beat Vera Zvonareva 7-5, 6-0 and Venus beating fellow American Lauren Davis in straight sets.

Serena Williams, seeking a sixth Australian and 19th Grand Slam title, saved three set points in the ninth game before holding to swing the momentum of the match.

She said Zvonareva, a two-time Grand Slam finalist who played only five tournamen