Tennis superstar Naomi Osaka has joined a growing sporting boycott over racial injustice, following protests in the US after another police shooting of a black civilian.

The Japanese ace posted an impassioned explanation of her reasons for withdrawing from the Cincinnati Masters, where she was due to appear in the semi-finals of the singles event.

Osaka, whose father is Haitian, wrote that “as a black woman I feel as though there are more important matters at hand that need immediate attention”.

Tweet from @naomiosaka

The two-time grand slam winner decried the “continued genocide” of black people at the hand of police, saying ongoing events were making her sick to her stomach.

Her decision comes after the NBA called off all of its three play-off matches scheduled for Wednesday.

The Milwaukee Bucks had earlier boycotted their match against Orlando Magic following the police shooting of Jacob Blake in the team’s home state of Wisconsin.

The NBA’s sister competition, the WNBA and the Major League Baseball has also joined the protest.

The Milwaukee Brewers and Cincinnati Reds are the first teams in Major League Baseball to boycott a game.

Tweet from @MLB

Osaka was due to play Belgium’s Elise Mertens after defeating Estonian Anett Kontaveit in the quarter-finals of the Cincinnati event.