MELBOURNE (AFP) - World No. 2 Andy Murray beat Portugal's Joao Sousa in four sets to reach the Australian Open fourth round on Saturday, apparently unaware of a medical drama involving his father-in-law on the adjacent tennis court.

The four-time finalist wore down the 33rd-ranked Sousa to win 6-2, 3-6, 6-2, 6-2 in two hours, 38 minutes, while Nigel Sears, father of his heavily pregnant wife, Kim, needed emergency medical treatment.

Sears, 58, who is also the coach of Ana Ivanovic, was treated by medics on a stairway and Ivanovic's match with Madison Keys on Rod Laver Arena was suspended for almost an hour before resuming.

Sears was later stretchered away and taken by ambulance to hospital and was said to be in a conscious state.

The Serb was leading 1-0 in the second set after taking the first 6-4 when play was suspended but eventually went down 4-6, 6-4, 6-4 to exit the tournament.

Ivanovic still appeared distressed when returning to court but tournament organisers said a discussion had taken place with both players before play resumed. They said the two women had been given the opportunity to consult their teams.

Murray will play the winner of the all-Australian clash between Bernard Tomic and John Millman in the fourth round.

The Scot left the Margaret Court Arena without doing the usual post-match on-court interview and it was announced he would not be doing a press conference.

Witnesses said he was met by his mother Judy upon leaving the court.

Murray broke Sousa twice to take the opening set, but lost his first set of the tournament as news filtered through of the ongoing drama in the stadium next door.

The world No. 2 asserted command in the third set with two more breaks and then made crucial breaks in the fifth and seventh games to dominate the final set.

Murray won through to the round of 16 in Melbourne for the eighth straight year, with the win stretching his record over Sousa to 7-0.