Andy Murray through at Australian Open after beating Joao Sousa

Andy Murray has been beaten three times in the Australian Open final

Andy Murray saw off Portugal's Joao Sousa in straight sets to earn a last-16 clash with Grigor Dimitrov at the Australian Open.

The British number one, seeded sixth, hit 39 winners on his way to a 6-1 6-1 7-5 victory at Melbourne Park.

His prize is a chance to amend for last summer's Wimbledon quarter-final defeat by Dimitrov when they meet on Sunday.

The Bulgarian 10th seed needed five sets to get past Marcos Baghdatis earlier on Friday.

Murray, 27, should not lack confidence after a third consecutive straight-sets win, despite allowing Sousa back into the third set from a break down.

The Scot urged himself to "Focus! Focus!" and the air of frustration grew when two match points slipped by. However, he converted the third two games later to win in two hours and six minutes.

"I was up two sets and 4-1 and Joao came back into it," said Murray. "He competed very well. He always does."

Sousa, 25, had lost to Murray in Melbourne two years ago but, now ranked 55 in the world, he expected to make it more of a contest this time.

Sixth seed Murray dominated the third round match against his opponent, ranked 55 in the world

Murray had other ideas, finding his way in the opening exchanges as a stiff breeze whipped around Hisense Arena, before going through his whole shot-making repertoire.

Two of his trademark backhands down the line set up break point in game four and the Briton crunched a cross-court backhand that left Sousa no chance.

Using the gusting wind to his advantage, Murray broke again two games later thanks to a clever dipping slice and the first set was wrapped up in 31 minutes.

Murray was well in control and he took a decisive step towards victory by winning a lengthy third game in the second set when Sousa fired long under pressure.

The Portuguese called for the trainer at 4-1 down, receiving attention to his left knee before grimacing in pain as the trainer worked on his quad.

There was little he could do on the resumption as Murray powered on, pressing for a break early in the third and finally getting it with another heavy backhand winner for 3-1.

There was a loud sympathetic cheer for Sousa when he finally got a second game in a set after 90 minutes, but Murray then unexpectedly helped out by allowing him back into the set.

A double fault and two loose forehands let a 40-15 lead slip and Murray was clearly furious with himself as he looked to coach Amelie Mauresmo and the rest of his team courtside.

The irritation only increased when he failed to capitalise on two match points at 5-4.

Any thoughts of a serious fightback were quickly stamped upon two games later, however, when Murray earned a third match point and watched as a Sousa lob drifted over the baseline.

"I think today was my longest match but I feel pretty good," Murray added.

"Normally towards the latter stages of this event, you tend to play more matches in the evenings, but so far I played three matches pretty much in the heat of the day.

"Thankfully they've not been too long and it hasn't taken too much out of me."