Australia opener Travis Head hit back at a majestic 160 from England's Joe Root on the second day of the fifth Ashes Test in Sydney.

Root's masterclass helped England to a competitive 384 at the Sydney Cricket Ground, but Head feasted on some woeful bowling to skip to an unbeaten 91 from 87 balls. Australia are 166-2 after 34.1 overs and have cut the deficit to 218.

The tourists had earlier lost 7-158, including a final collapse of 5-61 sparked by Jamie Smith's horrific dismissal.

Smith, who was caught off a no-ball and had other moments of fortune in his skittish 46, played a truly awful shot to be caught off part-time medium-pacer Marnus Labuschagne.

On a pitch that offered more for the bowlers on Monday, England's total felt around par, and Australia's batters made rapid inroads, helped by the tourists' attack and two dropped catches.

With new-ball bowlers Brydon Carse and Matthew Potts leaking runs, Jake Weatherald was put down twice as he and Head added 50 in 9.2 overs.

It took the belated introduction of captain Ben Stokes to trap Weatherald lbw, with Head then sharing another 105 with Labuschagne. Stokes and Labuschagne exchanged words before the England captain drew him into an edge to gully for 48.

Head remains, on course for his third century of the series. Of equal concern for England would have been the fitness of Root, but a spell off the field at the end of the day was later explained as cramp in his back.