Belinda Bencic continued her impressive run of form this season with a straight-sets win over Viktoriya Tomova in the opening round of the Qatar Open.

The seventh seed triumphed at the Abu Dhabi Open last week to add to her Adelaide International 2 success from January and is now seeking another title in Doha.

Bencic eased to a 6-0 6-1 win against Bulgarian qualifier Tomova and will face two-time tournament winner Victoria Azarenka for a place in the quarter-finals.

Maria Sakkari also advanced on Tuesday, overcoming Zheng Qinwen 6-2 3-6 6-3, as did fellow seeded player Daria Kasatkina with a 7-6 (7-5) 6-2 win against Rebecca Marino.

Zheng may have suffered an early exit, but last season's WTA Newcomer of the Year produced the shot of the tournament with a winning tweener en route to taking the second set.

Petra Kvitova, another two-time winner in Qatar, defeated Zhang Shuai 7-5 6-2, while Danielle Collins beat Elise Mertens 6-4 7-6 (8-6) and will now face top seed Iga Swiatek.

Second seed Jessica Pegula will take on Jelena Ostapenko, meanwhile, after the Latvian proved too strong for Madison Keys in a 7-5 6-2 victory.