American Jessica Hardy broke her own 50 meters breaststroke short course world record when she clocked 29.36 seconds at a World Cup meeting Saturday.
It was one of three world records broken on the second day of the two-day competition in Moscow.
The 22-year-old set the previous record of 29.45 at the first leg of the World Cup in Durban, South Africa, last month.
Russian Yevgeny Korotyshkin became the first man to go under 49 seconds in the 100 meters butterfly with a time of 48.99, breaking American Ian Crocker's five-year-old mark of 49.07.
South Africa's George Du Rand set the men's 200 meters backstroke record with a time of one minute 47.08 seconds. He improved the mark of 1:47.84 set by Austrian Markus Rogan at the world short course championships in Manchester in April 2008.
Two more world records were broken Friday, with Australia's Marieke Guehrer setting the mark in the women's 50 meters backstroke and Hungarian Evelyn Verraszto in the women's 200 meters medley.
A glut of world records have been set in recent months with swimmers using the polyurethane swimsuits, which will be banned by the sport's world governing body FINA from January 2010.
Moscow was hosting the second leg of the FINA World Cup with Stockholm stages the next leg on November 10-11.
