World No.1 Serena Williams has survived a tough early test to safely advance to the second round of the Australian Open at Melbourne Park.

The six-time champion needed one hour 45 minutes to see off Italian Camila Giorgi 6-4 7-5 in sweltering conditions on day one of the Open.

A knee injury had prevented Williams from completing a competitive match since the US Open in September, but the American came through unscathed to book a second-round meeting on Wednesday with either Latvian Jelena Ostapenko or Taiwan’s Su-Wei Hsieh.