MELBOURNE - DEFENDING champion Serena Williams opened her Australian Open campaign with a stuttering 6-3, 6-3 win over unseeded Australian Jarmila Gajdosova on Monday.

Williams, who stunned the tennis world by winning here last year ranked 81 in the world as she came back from injury, needed just over an hour to dispose of her unfancied opponent.

The American, known for making slow starts to tournaments then building momentum, was unfazed by a display that included 15 unforced errors and three double faults.

Williams began confidently and raced to a 3-0 lead as the 20-year-old Gajdosova displayed early nerves.

But a string of unforced errors from the seventh seed let Gajdosova back into the match, levelling the scores at 3-3 as the Melbourne Park crowd cheered on the adopted Australian, originally from Slovakia.

Struggling to find her radar, Williams yelled: 'What am I doing out here?', at one point tumbling over and falling heavily on the tournament's new Plexicushion surface.

The eight-time Grand Slam champion had to rely on her serve to get out of trouble, firing down an ace to take the first set 6-3 after 34 minutes.

Williams' vast experience eventually told and the 26-year-old champion snuffed out Gajdosova's resistance in the second set, breaking her three times to take the match and march into the second round.