Naomi Osaka loses to Marketa Vondrousova in women's singles tennis

Japanese superstar Naomi Osaka suffered a surprise exit in her home Olympics as Czech Marketa Vondrousova earned a straight-set win in Tokyo.

Osaka has been one of the faces of the Games in the Japanese capital and had the honour of lighting the Olympic cauldron in last week's opening ceremony.

But the four-time Grand Slam champion could not back that up by winning a medal, losing 6-1 6-4 to the world number 42 in the third round.

Osaka, who is the reigning US Open and Australian Open champion, had won 25 of her previous 26 matches on a hard court.

It was Osaka's first tournament after withdrawing from the French Open in June, when she revealed she had "suffered long bouts of depression" since winning her first Grand Slam title in 2018.

Osaka's exit follows that of Australian top seed Ashleigh Barty in the first round, leaving the women's singles draw wide open.