RIO DE JANEIRO: Former Olympic champion Venus Williams was eliminated in the first round at the Rio Games on Saturday after Belgian underdog Kirsten Flipkens mounted a spirited fight back to cause the biggest upset of the opening day.

Another notable casualty on the first day of competition was former world No. 1 Ana Ivanovic, who surged ahead in the first set against world No. 12 Carla Suarez Navarro but lost 2-6 6-1 6-2 after two error-strewn sets.

With US Secretary of State John Kerry and gymnastics gold medal favourite Simone Biles looking on, seven-times grand slam winner Williams won the first set but became frustrated as the match wore on, losing 4-6 6-3 7-6(5) to the world number 62.

Flipkens collapsed on to the court after winning the final set tie-breaker and the rowdy Brazilian crowd serenaded her with chants of “ole, ole, ole”.

Flipkens later thanked the “amazing” Brazilian crowd for helping her pull off one of the biggest wins of her career.

“To beat Venus Williams on the centre court, one of the biggest champions in our history, that (gave me) goosebumps all over the place,” she told reporters.

The loss will not be the end of the competition for 2000 Sydney Games champion Williams, however, as the 36-year-old is bidding to win her fourth doubles gold medal with sister Serena.—Reuters