Andy Murray moved into the fourth round of the Australian Opne, but was made to work against Portugal's Joao Sousa.

The British number one claimed a 6-2 3-6 6-2 6-2 victory in Melbourne, but the match provided a significant step-up in quality for Murray.

Murray was far from his fluent best on Margaret Court Arena but the world number two was clinical in the crucial moments as he sealed a four-sets victory.

The British number one played on apparently unaware that his father-in-law Nigel Sears had been taken to hospital after collapsing on Rod Laver Arena.

Murray had struggled for his usual rhythm during the match as he consistently mistimed his forehand and was regularly forced to rely on his second serve.

Sousa, however, was unable to capitalise as he carved out a number of early opportunities but each time watched Murray momentarily find his best to survive.

A scintillating cross-court forehand from the Scot saved a break point in the third game and then two irretrievable serves diverted another in the fifth as Sousa failed to make his strong start count.

It proved costly as Murray found his groove at 3-2, brilliantly hunting down and then flicking away a Sousa drop-shot to break the Portugese and move two games clear.

Frustrated, Sousa wavered from his baseline game, which suited Murray, who picked him off with ease and broke again to clinch the opening set.

The score, however, flattered the British number one and it was little surprise that Sousa, composing himself again, nicked the first break in the second when a Murray backhand flew long.

Sousa had a foothold and as Murray huffed and puffed, his opponent broke again to seal the set and level up.

When Murray appears most exasperated he often produces his most inspired tennis and that was the case in the third set, as he used his superior touch, craft and speed to outmanoeuvre Sousa.

Two breaks of serve put the Briton back in front and he carried his momentum into the fourth with another break at 2-2.

Sousa was suddenly on the back foot and he never looked like recovering as Murray raced away, breaking again at 5-2 before sealing victory in two hours and 38 minutes.

Murray will now face either Bernard Tomic or John Millman, both from Australia, in the last 16 next week.