GOLD COAST, Australia (AFP) - American Katie Ledecky broke her own world record in the 400m freestyle at the Pan Pacific Championships in Australia on Saturday.

The 17-year-old schoolgirl clocked 3min 58.37sec to beat her previous mark by 0.49sec.

Ledecky only broke the previous world record in the event at the US Championships on Aug 9 and continues her remarkable run of world records.

She holds the world records in the 400m, 800m and 1500m freestyle to make her the first woman since Janet Evans to hold all three records at the same time.

Ledecky's win in the 400m was her fourth gold medal of the Pan Pacific Championships on the Gold Coast after wins in the 200m and 800m freestyle and as part of the USA 4x200m freestyle relay.