Players swathed themselves in ice packs, one felt ill and another complained she couldn't breathe on Monday as soaring heat made for a gruelling first day at the Australian Open.

As temperatures rose to a sweltering 34 C (93 F), red-faced players sweated through afternoon matches at Melbourne Park and spectators dived for shade.

One fan sitting in the hot sun collapsed during Juan Martin del Potro's match against Adrian Mannarino, although medical workers blamed a pre-existing condition.

Play was halted while she was taken away for treatment.

Fernando Verdasco, a first-round loser to Australian teen Bernard Tomic, said he felt physically sick during their four-hour encounter. The Spaniard appeared unwell as he draped himself in a towel stuffed with ice.

"I started feeling nauseous on the court. I just think it was a lot of heat," said Verdasco, a veteran of 24 five-setters. "I've been in Perth and Auckland and not one day was this hot. So it was tough just to come here two days ago and go on court and play in these high temperatures."

Tomic admitted he regretted his decision to request a day-time match, saying he should have asked to play in the evening.

"Silly me," he smiled. "Did not know that the heat was going to be like this."

"I chose the wrong time to play. But luckily I won," he added.

Spectators donned floppy hats and sunglasses and slathered themselves in sun cream at the venue in central Melbourne, which is now in the middle of the southern hemisphere summer.

The Australian Open is frequently affected by high temperatures and there was consternation in 2009, when officials were reluctant to close the roof on Rod Laver Arena despite temperatures hitting 40 Celsius.

High temperatures are forecast to continue this week in Melbourne.