Major US sporting events were called off on Wednesday as athletes protested against racial injustice following the police shooting of Jacob Blake in Wisconsin last week.

Three NBA play-off games, three Major League Baseball matches, three WNBA fixtures and five Major League Soccer games were postponed after player-led actions in response to the shooting of African-American Blake and the civil unrest that has followed.

Tennis star Naomi Osaka also withdrew from her semi-final at the Western & Southern Open in New York, scheduled for Thursday, saying "before I am an athlete, I am a black woman".

And her decision was followed with an announcement the tournament – the last warm-up for the US Open for both men and women – would be put on hold on Thursday.

Blake was shot on Sunday in Kenosha, Wisconsin – 40 miles from Milwaukee – apparently in the back, and the incident was captured on phone video, igniting new protests over racial injustice in several cities.

Wednesday's multi-sport response began when the Milwaukee Bucks boycotted their play-off game against the Orlando Magic.

Leading 3-1 and needing just one more win to move into the Eastern Conference semi-finals, the Bucks did not emerge from their locker room for practice ahead of game five.

The NBA swiftly postponed its two other play-off games scheduled for Wednesday night between the Los Angeles Lakers and Portland Trail Blazers and the Houston Rockets and Oklahoma City Thunder.

Lakers talisman LeBron James tweeted: "F*** THIS MAN!!!! WE DEMAND CHANGE. SICK OF IT", while the Lakers later posted "#JusticeForJacobBlake".

Baseball matches between the Cincinnati Reds and Milwaukee Brewers in Milwaukee, the Seattle Mariners and San Diego Padres in San Diego, and the Los Angeles Dodgers and San Francisco Giants in San Francisco were also postponed.

"The players from the Brewers and Reds have decided to not play tonight's baseball game," players from both teams said in a joint statement.

"With our community and our nation in such pain, we wanted to draw as much attention to the issues that really matter, especially racial injustice and systemic oppression."

Mariners pitcher Justin Dunn tweeted: "Enough is enough."

The remaining major league matches scheduled for Wednesday were either in progress or just about to start when the announcements were made.

Former world No 1 Osaka later announced her withdrawal decision on Twitter, hours after qualifying for a semi-final against Belgium's Elise Mertens.

"Before I am an athlete, I am a black woman. And as a black woman I feel as though there are much more important matters at hand that need immediate attention, rather than watching me play tennis," wrote Osaka, who was born in Japan to a Haitian father and Japanese mother, but has lived in the US since the age of three.

"I don't expect anything drastic to happen with me not playing, but if I can get a conversation started in a majority white sport I consider that a step in the right direction.

"Watching the continued genocide of Black people at the hands of people is honestly making me sick to my stomach."

A few hours after Osaka's decision, both women's and men's tours plus the US Tennis Association (USTA) said the tournament would be paused for a day on Thursday.

"As a sport, tennis is collectively taking a stance against racial inequality and social injustice that once again has been thrust to the forefront in the United States," the three organisations said in a statement.

"The USTA, ATP Tour, and WTA have decided to recognise this moment in time by pausing tournament play at the Western & Southern Open on Thursday, August 27."

The WNBA followed the NBA's lead by also postponing its three scheduled Wednesday matches, before Major League Soccer announced the postponement of five of its six scheduled fixtures.

Bucks senior vice president Alex Lasry wrote on Twitter: "Some things are bigger than basketball. The stand taken today by the players and org shows that we're fed up. Enough is enough. Change needs to happen.

"I'm incredibly proud of our guys and we stand 100% behind our players ready to assist and bring about real change."

The NBA said in a statement on its Twitter account that the league and the National Basketball Players Association were announcing that "in light of the Milwaukee Bucks' decision to not take the floor today for Game 5 against the Orlando Magic, today's three games – MIL-ORL, HOU-OKC and LAL-POR have been postponed. Game 5 of each series will be rescheduled".

The Bucks, whose star man Giannis Antetokounmpo was named defensive player of the year this week, are among the favourites to collect only the second NBA championship in their history.