Holland's Pieter van den Hoogenband shattered the World 100metres freestyle record at the Olympic Games in Sydney on Tuesday.

The 22-year-old, who equalled his own world mark when winning the 200m freestyle title on Monday, became the first swimmer to break the 48-second barrier.

Van den Hoogenband clocked 47.84 secs in his semi-final to take 0.34 off the record set by Australia's Michael Klim on the lead-off leg of the 4x100m relay in Sydney just three days ago.

The Maastrict-based swimmer's record breaking display kept him on course to dethrone Russia's Alex Popov - champion for the past two Olympics - in tomorrow's final.

Popov, bidding to become the first man to win the coveted title three Games in succession, was second in the other semi in 48.84 with Klim winning in 48.80.

It was the ninth world record in just four days of competition at the International Aquatic Centre while there have also been 19 Olympic records broken.

Van den Hoogenband, who beat Australia's 17-year-old hero Ian Thorpe in the 200m, could also complete a Games hat-trick in the 50m freestyle.

Australia's Susie O'Neill also won the first leg of her treble bid with victory in a thrilling 200m freestyle final that delighted another 17,000 crowd still coming to terms with Thorpe's unexpected defeat.

The 27-year-old, fifth at the Games four years ago, won in one minute 58.24 seconds from Slovakia's Martina Moravcova (1:58.32) with Costa Rica's Claudia Poll third (1:58.81).