Zheng Jie of China rests on a bench during a medical timeout during her match against Casey Dellacqua of Australia. Picture: Reuters/Petar Kujundzic

Melbourne – China's Zheng Jie described how she felt sick and had palpitations before needing medical treatment for heat stress in worrying scenes at the Australian Open on Friday.

The 2010 semi-finalist, playing during one of Melbourne's most severe heatwaves, said she couldn't focus and was hitting the ball randomly during her loss to Casey Dellacqua.

“I felt so hot, my mind wasn't working. I was looking at the ball, but I couldn't focus on it. Then I couldn't concentrate. This weather is very difficult for me,” she said.

Zheng, 30, lay down and was rubbed with ice and had her pulse checked before continuing against the local favourite, eventually losing 6-2, 6-4.

She is just one of many casualties of temperatures over 40 degrees Celsius this week, which prompted organisers on Thursday to take the rare step of suspending play on the outside courts.

Jamie Murray, brother of Wimbledon champion Andy, was another victim when he went down with heat stroke and body cramps after his doubles match before play was halted on Thursday.

“When it happens the first time, it's pretty scary... he was struggling for a good three, four hours after the match,” Andy Murray said.

Other players have fainted and vomited and a ball boy collapsed. State emergency services minister Kim Wells told The Age newspaper that 1,000 spectators were treated for heat exhaustion in one day.

Organisers have defended their decision to let play continue for most of the week in the face of bitter complaints. Frank Dancevic, who blacked out during his match, called conditions “inhumane”.

But chief medical officer Tim Wood told the BBC: “We evolved on the high plains of Africa chasing antelope for eight hours under these conditions.

“There will be some players who complain and no one is saying it is terribly comfortable to play out there, but, from a medical perspective, we know that man is well adapted to exercising in the heat.

“Whether it is humane or not is a whole other issue.”

After four days of intense heat, a cooler change blew in on Friday evening, dropping the temperatures by nearly 20 degrees Celsius. – Sapa-AFP