World number one Andy Murray reached the last 16 of the Barcelona Open without striking a ball on Wednesday after Bernard Tomic withdrew from the tournament due to a back injury.

Murray was due to come up against Tomic at the Real Club de Tenis Barcelona 1899 on day three of the clay-court event, but the Australian pulled out on the morning of the second-round match.

Three-time grand slam champion Murray will face Albert Montanes or Feliciano Lopez in round three.

Murray is eyeing his second title this year, having been dumped out of the Monte-Carlo Masters by Albert Ramos-Vinolas in the round of 16 last week.

There was no word on how long Tomic, who has not lost all four matches against Murray, will be sidelined.