Defending champion Clijsters sails into round two

Belgium's Kim Clijsters began her Australian Open defence with a straight-sets win over Portugese qualifier Maria Joao Koehler on Monday.

Clijsters won a surprisingly close first set before racing away with the second to win 7-5, 6-1, showing no signs of the hip injury that forced her out of the Brisbane International two weeks ago.

The 2011 champion was forced to work hard in the early stages by the unknown Koehler, who was playing her first ever main tour match outside Portugal.

The 19-year-old from Porto only managed to land 35 percent of her first serves in the opening set but scrapped hard for every point, playing well above her world ranking of 223.

But, when serving at 5-6, her lack of experience told and Clijsters attacked, quickly racing to love-40, then wrapping up the first set courtesy of a Koehler double fault.

Clijsters seized control and broke twice more in the second set to cruise to a comfortable win.

"I'm feeling good and I'm happy to say that (the injury) is all behind me," the 28-year-old world number 14 said.

"I've always loved coming to Australia and that feeling is stronger after last year. Being on this court brings back a lot of memories."

With 2011 runner-up Li Na also winning on Monday, last year's finalists remain on course for a blockbuster fourth-round showdown.