Andy Murray made relatively confortable progress as news broke about his father-in-law ©Getty Images

Britain's world number two Andy Murray survived a second-set wobble to overcome Portugal's João Sousa in the third round of the Australian Open on a day overshadowed by his father-in-law Nigel Sears collapsing at the Rod Laver Arena in Melbourne. 

The 58-year-old Sears is one of Britain's leading coaches and was in the Australian city working with Serbia's Ana Ivanovic. 

He had been watching his Ivanovic compete against American opponent Madison Keys when the incident occurred.

Proceedings were delayed for almost an hour before he was removed from the court on a stretcher.

Murray, who overcame 32nd seed Souza 6-2, 3-6, 6-2, 6-2 on the Margaret Court Arena, did not know what had happened during the match but immediately departed for the hospital afterwards, cancelling his post-match news conference.

"It was tricky, I didn't feel I was in a great rhythm and wasn't hitting the ball cleanly at the start," he said later in a statement released by tournament organisers.

"He was hitting the ball great, close to the lines, and making me do a lot of running."

Ana Ivanovic's coach and Andy Murray's father-in-law Nigel Sears was carried from the court on a stretcher ©Getty Images
Ana Ivanovic's coach and Andy Murray's father-in-law Nigel Sears was carried from the court on a stretcher ©Getty Images

Sears, a former captain of the British Fed Cup team, is in his second spell working with Ivanovic after he was reappointed her coach last July.

Sears, whose daughter Kim is married to Murray and is expecting the couple's first child next month, is reportedly now "conscious, talking and sitting up" in hospital.

Murray will face home star and 16th seed Bernard Tomic in the fourth round after he beat compatriot John Millman 6-4, 7-6, 6-2 in the last match of the day.

It was a day of few shocks in the men's singles draw, with fourth seed Stanislas Wawrinka, eighth seed David Ferrer and 10th seed John Isner all enjoying comfortable progress.

Switzerland's Wawrinka, the champion in 2014, beat Czech Republic's Lukas Rosol 6-2, 6-3, 7-6, while Spain's Ferrer overcame American Steve Johnson 6-1, 6-4, 6-4 and Johnson's fellow countryman Isner got the better of Spaniard Feliciano Lopez 6-7, 7-6, 6-2, 6-4.

There was disappointment for Ivanovic, meanwhile, following the delay, after she lost 4-6, 6-4, 6-4 to Keys.

She had been leading 6-4, 1-0 at the time of the incident involving Sears.

Ivanovic's second round win over Latvia's Anastasija Sevastova had also been delayed when a spectator fell down a flight of stairs.

Third seeded Spaniard Garbine Muguruza also crashed out, losing 6-3, 6-2 to Czech Republic's Barbora Strycova.