June 29 (Reuters) - Gretchen Walsh ⁠broke the women's 50 metres freestyle world record on Sunday at ⁠the Sette Colli International Trophy in Rome, lowering a mark ‌that had already been beaten this month.

The 23-year-old clocked 23.55 seconds, breaking the previous record of 23.59 set by fellow American Kate Douglass earlier this month at a U.S. ​Pro Swim Series event in Indianapolis.