Fourth seed Simona Halep overcame a gutsy display from Elise Mertens to secure her place in the Australian Open quarter-finals with a 6-4 6-4 win.

The 2018 finalist was a break up in the first set and two breaks up in the second but saw her advantage eroded by the Belgian 16th seed in both sets.

However, Halep responded by moving up gears, and eventually won in one hour 37 minutes on Rod Laver Arena.

The Romanian will play Estonian Anett Kontaveit in the last eight.

Mertens adopted a higher-risk strategy in the match, where she produced more winners but also more errors - 38 to Halep's eight. But she still pushed Halep to the limit, which reminded the Romanian of their encounter in 2019.

"I played Elise in the Doha final last year - I led by a set and was up 4-2 but lost the match," said Halep, who has yet to drop a set in Melbourne this year.

"I knew I had to stay focused today. I was a little nervous at 4-3 but was strong enough to finish."

Halep gestured to her box on occasions. The Wimbledon champion had previously revealed she would be donating A$200 (£104) to bushfire relief every time she gave her Australian coach Darren Cahill a hard time.

"Darren is counting the looks," she said. "Was I worse than the last match? Yes. But it's for a good cause. He said he would tell me the total at the end of the tournament."

Kontaveit, the 28th seed, held off a superb deciding-set fightback from 18-year-old Iga Swiatek to reach her first Grand Slam quarter-final.

Pole Swiatek, who surprised 19th seed Donna Vekic in the previous round, looked confident both on the baseline and at the net in the first two sets and even produced a tweener during the second set.

But her form dropped at the start of the third and she was 5-1 down and heading for the exit. However, she fought back brilliantly to level before Kontaveit stopped the rot by holding serve before sealing victory by breaking her opponent.

Spaniard Garbine Muguruza is into her first Grand Slam quarter-final for two years following a 6-3 6-3 win over Dutch ninth seed Kiki Bertens.

The 26-year-old, who saw off fifth seed Elina Svitolina in the third round, showed glimpses of the sort of form that led her to the French Open and then the Wimbledon title in successive years.

She will now play either German 2016 champion Angelique Kerber or Russian 30th seed Anastasia Pavlyuchenkova.