SANTA CLARA, California (AFP) - Australia's Cate Campbell set a US Open record of 53.30 in winning the women's 100m freestyle at the Santa Clara International Grand Prix swimming meeting.

Natalie Coughlin was second, improving her own American record with a time of 53.39.

Campbell also led off an Australia squad that captured the women's 4x100m free relay with a time of 3:43.08.

There was a strong showing for Australia's women in the 400m free as well, with Bronte Barratt and Kylie Palmer finishing one-two. Barratt took home gold with a meet record of 4:04.57. Palmer was second in 4:05.98 ahead of American Kate Ziegler (4:07.11).

A total of four meet records fell during the first full day of competition.

Brendan Hansen won gold in the men's 100m breast with a meet-record time of 1:00.01. Slovenia's Damir Dugonjic was second in 1:01.67 and Japan's Ryo Tateishi was a close third in 1:01.68.

Swimming superstar Michael Phelps, preparing for a record-breaking bid at the Beijing Olympics in August, took home his first gold of the meet with a win in the men's 400m individual medley.

Phelps led throughout the race and finished with a time of 4:13.47. Robert Margalis was second in 4:15.05.

Japan's Izumi Kato won the women's 200m breaststroke in 2:27.69, ahead of former world record-holder and reigning Olympic champion Amanda Beard (2:28.15).

The men's 4x100m free relay saw a strong South African squad of Lyndon Ferns, Roland Schoeman, Gideon Louw and Ryk Neethling win in 3:15.58.

The meet continues Saturday with 10 events.