World number one Simona Halep marched into the quarter-finals of the Madrid Open with a straight-sets victory over Kristyna Pliskova.

Halep has won the title in each of the last two years at the Caja Magica and moved a step closer to three in a row with a 6-1 6-4 third-round victory.

The top seed gave Pliskova the runaround in the first set, but was made to work in the second on a hot day as she stretched her winning run in the Spanish capital to 15 matches.

Halep will either face Pliskova's twin sister, Karolina, or Sloane Stephens in the last eight following another relentless performance on Manolo Santana Stadium.

The sprightly Halep lost only four games in the first two rounds and started with great intensity on Wednesday, breaking to take a 3-1 lead when qualifier Pliskova netted a forehand.

Halep raced through her service games and Pliskova, playing with a strapped right thigh, was unable to halt her momentum, the rampant Romanian going a double break up before ending the first set with an ace.

Pliskova channelled her frustration well to ask more questions of the defending champion in the second set, but Halep rallied from 0-40 down and saved four break points to level at 1-1.

The 94-ranked Czech had another opportunity to break for a 5-3 lead, but a defiant Halep held again after an errant backhand from Pliskova that she ought to have put away 

It was the clinical Halep who claimed the decisive break of the second set to go 5-4 up and she was soon pumping her first following a hold to love, sealing another impressive victory by stooping to whip away a classy forehand from just beyond the baseline.