Unfancied Kori Carter outstripped US teammate Dalilah Muhammad for gold in the womens 400m hurdles at the world championships on Thursday.

"I just had to run my race, go out and let them chase me," said the 25-year-old Carter.

"I'm on top of the world right now, it's been such a long year."

Jamaica's Ristananna Tracey timed a personal best of 53.74sec for bronze, while two-time defending champion Zuzana Hejnova of the Czech Republic was fourth.