Play on the outer courts in Melbourne was halted until late afternoon, with the delay later extended by an extra hour, as temperatures exceeded 40 degrees Celsius (104 Fahrenheit) for a third successive day. Only the two main courts, protected from the sun by retractable roofs, remained in service during Thursday's delay.

"FINALLY!!!! Play suspended because of the heat… Heat policy should have been in two days ago already.. #burning #crazy #nothealthy," Belgian player Kirsten Flipkens wrote on Twitter after the announcement. She was on court with doubles partner Kiki Bertens when play was halted.

On all courts, the current set was completed prior to the shutdown - with the same natural break in play being used to close the roofs on the Rod Laver and Hisense Arenas.

Third seed Maria Sharapova of Russia went the distance in the heat at the Rod Laver Arena as the tournament's "Extreme Heat Policy" was implemented during her final set against Italian Karin Knapp. Sharapova proceeded 6-3, 4-6, 10-8, playing another 50 minutes after the delay to complete the marathon third set. Sharapova is to face Alize Cornet of France, who beat Camila Giorgi in three sets, in the next round.

Unseeded qualifier Michael Berrer was the only German scheduled to play on Thursday; his encounter with 26th seed Feliciano Lopez had not yet begun and was scheduled for one of the outside courts.

The heat wave is expected to endure for at least another day and has prompted complaints from several high-profile players, including Germany's Sabine Lisicki, who slumped to a three-set defeat on Wednesday.

US player Vavara Lepchenko, like Lisicki, visibly wilted in the high temperatures on Thursday. After winning the opening set 6-4 against Romanian 11th seed Simona Halep, Lepchenko went on to lose the next two 6-1 and 6-0. She required medical treatment during the second set, saying afterwards: "They definitely should have just not started the matches in the first place.

msh/pfd (AP, dpa, Reuters)