Former world No.1 Garbine Muguruza and Swiss sixth seed Belinda Bencic are safely through to the Australian Open third round on a rain-marred day four.

Muguruza ousted Australian hope Ajla Tomljanovic 6-3 3-6 6-3 in a two-hour, 20-minute battle while Benic had a straight-sets win over Jelena Ostapenko.

Muguruza, a former French Open and Wimbledon champion, is looking to scale the rankings after slumping to world No.32.

The Spaniard has been battling a viral illness which forced her to withdraw in the Hobart quarter-finals but looked back to full fitness on Thursday, blasting 34 winners against Tomljanovic.

The match was halted in the third set while officials closed the Rod Laver Arena roof but 26-year-old Muguruza held her nerve.

“It was a tough battle, we both fought until the end,” said Muguruza, who has reunited with coach Conchita Martinez.

“She is an aggressive player and I knew she was going to hit good shots and serves and not lose my patience.

“It was a tricky match.”

Muguruza’s next opponent will be either fifth-seeded Ukrainian Elina Svitolina or American Lauren Davis.

Bencic didn’t have it all her own way against Ostapenko, the 2017 French Open champion, before she prevailed 7-5 7-5.

Reaching last year’s US Open semi-finals as well as the final four at the WTA Finals, Bencic has been on the rise after a wretched run with injury.

The 22-year-old will play either Estonian 28th seed Anett Kontaveit or Spaniard Sara Sorribes Tormo on Saturday for a place in the last 16.

In other early action, Croatian 19th seed Donna Vekic enjoyed a routine 6-4 6-2 win over France’s Alize Cornet.

Bencic and Vekic are slated to meet in the fourth round.