World 800m champion Caster Semenya ran a season's best time of 1 minute, 59.90 seconds to easily win her third comeback race here on Sunday as she rebuilds her career after her sex test ordeal.

The 19-year-old South African was back at Berlin's Olympic Stadium, where she won her world crown last August, only for the sport's governing body, the IAAF, to demand a gender test into her abnormally high levels of testosterone.

Having only been cleared to race again last month, Semenya looked comfortable at the World Challenge meet, her third since her comeback, and dipped below two minutes for the first time since coming back.

She attacked in the last 100 meters and breezed past second-place Cherono Koech of Kenya and third-place Italian Elisa Piccione Cusma, even though Cherono ran a personal best of 2 minutes, 00.40 seconds.

"It feels good to be back in Berlin," said the teenager.

"I did not think about everything that happened after my gold medal, I just concentrated on my race and my time."