Dinara Safina continued her magnificent form by ending Serena Williams' 17-match unbeaten run at the German Open.

The Russian, who beat world number one Justine Henin on Thursday, saw off Williams 2-6 6-1 7-6 (7-5) to secure a semi-final against Victoria Azarenka.

After dropping the first set, Safina dominated the second and edged the decider after letting a lead slip.