Rome, Aug 3 (DPA) The final session at the Foro Italico at the world swimming championships in Rome saw four world records being broken to take the tally for the eight-day meet to an incredible 43.

The US 4x100m individual medley relay team consisting of Aaron Peirsol, Eric Shanteau, Michael Phelps and David Walters broke their own world record in the final swim of the tournament here Sunday.

The first two swims of the session also saw two world records with Briton Liam Tancock and Russian Yuliya Efimova, who managed to set new best marks in the men's 50m backstroke and the women's 50m breaststroke respectively.

Also getting a world record was Germany's Britta Steffen in the women's 50m freestyle.

The US medley relay team won in a time of 3:27.28, beating their own world record time of 3:29.34 which they swam in Beijing.

Germany finished second in a time of 3:28.58, with anchor man Paul Biedermann managing to just move ahead of Matthew Targett, who took the Australian team home in 3:28.64.

Germany's Queen of the sprints Steffen added the 50m freestyle title to her world championship 100m freestyle gold she won earlier in the week.

Steffen, who already achieved a sprint-sweep at the Olympics in Beijing last year, won in a world record time of 23.73, beating the 23.96 Marleen Veldhuis swam in April.

Sweden's Therese Alshammar won the silver medal in a time of 23.88, while Briton's Cate Campbell and Marleen Veldhuis both took the bronze medal with a time of 23.99.

American 42-year-old Dara Torres, who finished eighth in the final, paid a tribute to Steffen after the race. 'She is an incredible athlete and that is a terrific time. It will stand for years.'

Steffen said that she did not expect to win. '50m is like a lottery. I was really surprised that I managed to get the gold. My aim was to swim a 23.8. The nice thing about swimming over this distance is that it is not sore to swim one lap, it is a lot of fun. I was simply lucky.'

Tunisian Oussama Mellouli repeated his Beijing success in the men's 1,500m, winning in a time of 14:37.28 to beat Ryan Cochrane, who lead for much of the race.

The Canadian finished in a time of 14:41.38. China's Sun Yang won the bronze medal, 9.56 seconds behind Mellouli.

In the women's 400m individual medley Hungarian Katinka Hosszu, who went into the race with bronze medals from the 200m butterfly and 200m IM, added gold in a time of 4:30.