Ana Ivanovic has lost a dramatic centre-court Australian Open clash with Madison Keys, which finished after an interruption of play when the Serbian's coach collapsed in the stands at Rod Laver Arena.

Ivanovic was leading 6-4, 1-0 in the second set of the third round match when coach Nigel Sears — the father-in-law of men's tennis star Andy Murray — appeared to fall while returning to his seat.

Play was suspended while Sears received medical attention.

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He was taken to hospital but tournament organisers said that he was breathing, conscious and talking to medical staff, and was treated by a cardiologist.

Murray, who was playing 32nd seed Joao Sousa on Margaret Court Arena, continued to play while the medical emergency unfolded on centre court.

Television microphones picked up Ivanovic talking to chair umpire Felix Torralba that she thought the person being treated was her coach.

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The Serb looked visibly distressed before she and Keys went off court about 10 minutes after play was halted.

Ivanovic still appeared distressed when returning to court almost an hour later.

"The match was suspended and the players updated on his condition. The players had the opportunity to consult with their teams and then went back on court," organisers said in a statement.

Keys managed to take out the match after the interruption, beating Ivanovic 4-6, 6-4, 6-4.

Women's Seeds: Day Six Garbine Muguruza Blanco [3] def by Barbora Strycova 6-3, 6-2

Garbine Muguruza Blanco [3] def by 6-3, 6-2 Angelique Kerber [7] def Madison Brengle 6-1, 6-3

def Madison Brengle 6-1, 6-3 Karolina Pliskova [9] def by Ekaterina Makarova [21] 6-3, 6-2

Karolina Pliskova [9] def by 6-3, 6-2 Victoria Azarenka [14] def Naomi Osaka 6-1, 6-1

def Naomi Osaka 6-1, 6-1 Madison Keys [15] def Ana Ivanovic [20] 4-6, 6-4, 6-4

Sears is the father of Murray's wife Kim, who is expecting their first child in mid-February and has not travelled to Melbourne.

The 58-year-old had previously coached Slovakia's Daniela Hantuchova, leading her to a top-10 ranking.

He joined Ivanovic in June 2011 after almost five years with the Lawn Tennis Association and Britain's Fed Cup team.

They parted company after Wimbledon in 2013 but he rejoined her team last year.

It was Ivanovic's second match in a row interrupted by a medical emergency.

She was left badly shaken when an elderly spectator fell on a flight of stairs during her match in the same arena on Thursday.

In a late match, China's Zhang Shuai defeated American Varvara Lepchenko 6-1, 6-3.

ABC/Wires