Rome - There was an unusually slow start to Saturday's evening session of the swimming world championships at the Foro Italico in Rome.

Unlike previous sessions that has seen a flood of world records, the first five swims of the evening produced only one world best mark.

Zimbabwean Kirsty Coventry, who was hoping to win at least three medals at this competition, finally picked up her first when she took the 200m backstroke in a world record time of 2:04.81.

She beat Russian Anastasia Zueva by .13 seconds. The bronze medal went to American Elizabeth Beisel in a time of 2:06.39.

Brazilian Cesar Cielo Filho showed why he is considered the best sprinter in the world when he added the gold in the 50m freestyle to the 100m gold that he won earlier in the competition.

Cielo Filho swam a championship record to beat France's Frederick Bousquet (21.21) and Amaury Leveaux (21.25) into second and third place.

In the women's 50m butterfly, Australian Marieke Guehrer was a surprise winner in a time of 25.48, beating Zhou Yafei by nine hundredth of a second.

Third place went to Norwegian Ingvild Snildal, who was a further hundredth behind.

Guehrer was totally shocked when she got out of the water. "Are you sure that I won, it must be a mistake. They must have made a mistake," she asked an Australian swimming official.

In the semi-finals of the women's 50m breaststroke Australian Sarah Katsoulis led the field into the final with a time of 30.33, beating Annamay Pierse by seven hundredth of a second.

Still on the programme for Saturday evening are the finals of the men's 100m butterfly, women's 800m freestyle and 4 x 100m medley, as well as the semi-finals in the women's women's 50m freestyle and men's 50m backstroke.(dpa)