Rome  - Serbian Milorad Cavic topped the heats in the men's 50-metre butterfly at the world championships in the Foro Italico on Friday, while there was disappointment for 42-year-old Dara Torres as she was eliminated from the women's 50m butterfly.

Cavic, who maintains that he beat superstar Michael Phelps at the Beijing Olympics, but that the timing was faulty to give the American victory, swam a 50.56, beating American Tler McGill into second place by 0.34.

Phelps, who swam two heats later, was on course to beat his own world record at the turn, but then eased off but still comfortably won his heat in 50.90 to register the third-fastest time.

In the women's 50m butterfly, Torres was eliminated with the 17th fastest time, just five hundredths behind Daniela Samulski, who was the slowest qualifier for the semi-finals.

Sweden's Therese Alshammar managed to beat her own championship record with the fastest qualifying time in 25.44, beating the 25.58 of Dutch world record holder Magdalena Veldhuis.

Alshammar's previous record stood at 25.82.

Brazilian Cesar Cielo Filho, who on Thursday won the men's 100m freestyle in world record time, broke the championship record in the 50m freestyle, when he qualified for the semi-finals with a time of 21.37.

Sweden's Stefan Nystrand had the second-fastest time, 0.19 off the pace, while world record holder Frederick Bousquet was third in the rankings in 21.63.

The heats of the men's 4x200m freestyle relay, as well as the women's 200m backstroke and the 800m freestyle will be swum later in the morning session.

On Friday evening, the finals of the women's 100m freestyle, 200m backstroke and the 4x200m freestyle relay, as well as the women's 100m freestyle, the 200m breaststroke will be swum.

The championships, which started on July 17, ends Sunday. (dpa)