Open officials yesterday applied the extreme heat policy for the first time this week at Melbourne Park as temperatures soared above 40 degrees for the third day in a row.

But its implementation was of no use to Bellucci, who was forced to play on - albeit under a closed roof at Hisense Arena - after dropping the first set against French 10th seed Jo-Wilfried Tsonga.

Bellucci, a qualifier who'd already played four matches before his third- round encounter with Tsonga, eventually departed, physically spent, with a 7-6 (8-6), 6-4, 6-4 loss.

"Every point I was thinking to give up," he said.

"But anyway I was fighting to at least end the match. When I lost the first set, it was very hard for me to win three more sets so I was just playing because I didn't want to retire.

"I was very tired and it was impossible to beat him in four or five sets."

Asked if he thought the heatwave conditions made it too dangerous to play, the battered Brazilian said it was "too much" to say someone could die.

"But I think for the players, we already play a lot of tournaments and a lot of matches, and to play in these conditions I think is not fair for the players," he said. "I think we should start later, like 5 or 6 o'clock, and then that should be better for the players and the crowd."

At the very least, Bellucci felt the roof should have been closed before the start of play, given the forecast of 44 degrees in Melbourne yesterday.

Tournament referee Wayne McKewen opted to enforce the extreme heat rule at 1.52pm following ongoing consultation with meteorological and medical staff.

Matches already under way on the outside courts were suspended at the end of the set in play, while no practice was allowed outside during the stoppage.

Play resumed on all outside courts at 6pm, but 12 matches scheduled for day four were cancelled.

Women's third seed Maria Sharapova and unseeded Italian Karin Knapp endured the worst of the conditions, slugging it out for almost 3 1/2 hours at Rod Laver Arena, with the roof open for the entirety.