Serena Williams has beaten Petra Kvitova in straight sets at the WTA Championships in Istanbul.
The world number one came through 6-2 6-3 to seal her place in the next round.
Williams's serve was accurate throughout the opening set and she wrapped it up 6-2 without any fuss.
In the second however, the Czech battled back and earned herself several break point opportunities early on.
Williams was able to save them though, and found her form towards the end of the match, powering several forehand winners past her opponent.
The win means that Williams is unbeaten so far in the tournament and now advances from the group stage.
