Azarenka collapses on court

Victoria Azarenka collapsed on court and was taken to hospital after experiencing headache-like symptoms in the searing heat during her second round match against Argentina's Gisela Dulko.

The No 10 seed, wearing a black dress in temperatures nearing 32 degrees Celsius, slumped to the ground while trailing Dulko 5-1 on the Grandstand court.

The 21-year-old Belarussian received medical treatment on the court before being taken away in a wheelchair as a medical official checked her pulse. She was taken by ambulance to a nearby hospital.

US Open tournament referee Brian Earley explained what had happened and added: "Out of respect for her privacy, we cannot give any more details. However, we can say that this does not seem to be primarily a heat-related illness."

Azarenka appeared to struggle as early as the third game when the trainer was called. She received treatment to her arm but also complained of blurred vision. It became increasingly clear that she was in difficulty as she took time out between every subsequent point and was ill at ease on her feet.

Then, while serving for the fourth time in the match, she collapsed on the baseline, leading to gasps from the crowd.

"I was scared," Dulko said after witnessing her opponent's collapse. "She went to the floor, I was worried for her. I went to see her, brought her some ice, did whatever I could to help."