World No.1 Naomi Osaka has been beaten in her opening match at the Dubai Duty Free Tennis Championships, losing to France’s Kristina Mladenovic 6-3 6-3 after winning last month’s Australian Open.

Japan’s Osaka, who parted ways with coach Sascha Bajin last week following her victory in Melbourne, struggled with her service game on Tuesday.

She won 48 per cent of her first serve points and made 25 unforced errors, folding in just over an hour.

Mladenovic hit three fewer winners than Osaka’s 19.

However the Frenchwoman made just nine unforced errors and converted seven of the 10 break point opportunities she carved out en route to registering her first career victory over a reigning world No.1.

Mladenovic, who is ranked 67th in the world, faces Spain’s Carla Suarez Navarro in the round of 16.

Suarez Navarro beat China’s Shuai Zhang earlier on Tuesday.