Serena Williams says she "did not choke" after missing four match points before succumbing to Czech seventh seed Karolina Pliskova in a dramatic Australian Open quarter-final.

Axar.az reports citing BBC, The 37-year-old American, going for a record-equalling 24th Grand Slam singles title, led 5-1 in the decider but lost 6-4 4-6 7-5.

Pliskova, 26, won the last six games after taking her third match point.

"I think she just played lights out on match points," Williams said.

Former world number one Pliskova will meet Japan's Naomi Osaka in Thursday's semi-finals.

Williams, seeded 16th, played down an ankle injury which she suffered during the rally as she missed her first match point when serving at 5-1, 40-30.

The seven-time Australian Open champion did not win another point on serve after the incident.

"She was hitting lines and went crazy. She played unbelievable on match points," Williams said.

"It was nothing to do with my ankle. Obviously I made some mistakes but she played really well."

Williams' inability to seal victory means a highly anticipated rematch of her controversial US Open final defeat by 21-year-old Osaka must wait.

Like fourth seed Osaka, Pliskova will be playing in the Melbourne last four for the first time.

She is one more victory from her second Grand Slam final, following defeat by Germany's Angelique Kerber in the 2016 US Open.

Pliskova had led by a set and a break at 3-2 before the momentum swung to Williams, who won nine games out of 10 as victory appeared a formality.

The momentum then swung back again to Pliskova in a chaotic encounter.

"I was almost in the locker room but now stand here as the winner," she said.

"My mind was in the locker room at 5-1 down but I was still here. I was too passive and mentally down. She got a little bit shaky in the end. I took my chances and I won.

"Naomi Osaka is dangerous but there is nobody more dangerous than Serena."