MELBOURNE (AFP) - British sixth seed Andy Murray ousted Portugal's Joao Sousa in straight sets to reach the fourth round at the Australian Open on Friday.

Murray won 6-1, 6-1, 7-5 in 2hr 6min and will face Bulgarian 10th seed Grigor Dimitrov in the round of 16.

Murray, a three-time runner-up in Melbourne, was always in command and broke the Portuguese's service seven times while dropping his serve only once.

He hit 39 winners, made only 18 unforced errors and won 83 per cent of his first serves.

Murray has now reached the round of 16 for the seventh consecutive year as he bids to track down an elusive Australian title after losing to Roger Federer in the 2010 final and Novak Djokovic in 2011 and 2013.

"I lost to Roger and to Novak a couple of times against some of the best-ever players here and playing in front of a packed arena here is always fun," Murray said.

"Grigor has improved a lot over the last couple of years and it should be a fun match."