The University of Melbourne has continued its reign as the top Australian institution in the most prestigious world rankings.

But it coincides with a warning that Australia's future success is "not guaranteed" due to the impressive rise of Asian universities.

Six Australian universities finished in the top 100 of the Times Higher Education world university rankings, which were released on Thursday.

The University of Melbourne was again ranked 33rd, followed by the Australian National University (47th), the University of Queensland (equal 60th), the University of Sydney (equal 60th), Monash University (74th) and the University of New South Wales (78th).