China's state television kept the NBA's season-opening games off the air on Wednesday in the latest fallout from a row over a team executive's support for pro-democracy protests Hong Kong.

The blackout added to an unusual start to the NBA season, as activists distributed t-shirts in support of Hong Kong pro-democracy protesters outside the arenas in Los Angeles and Toronto.

The NBA has a massive fan base in China and CCTV has traditionally shown the season openers.

But the games featuring the Toronto Raptors against the New Orleans Pelicans and the Los Angeles Clippers against city rivals the Lakers were not shown on the Chinese network on Wednesday morning (Tuesday night in North America).

Chinese internet giant Tencent, however, showed the two games on its streaming service.

CCTV and Tencent had cancelled their broadcasts of two NBA pre-season games held in China earlier this month after Houston Rockets general manager Daryl Morey tweeted "Fight for freedom, stand with Hong Kong."

CCTV had also warned that it would "investigate" its cooperation with the NBA.

Hong Kong has been rocked by months of demonstrations by citizens who accuse Beijing of chipping away at its freedoms. China has portrayed the protesters as violent separatists and bristled at what it calls "foreign interference" in the matter.

The backlash in China against Morey's comments cast a cloud over the NBA's lucrative broadcasting, merchandising and sponsorship interests in the country, where it has legions of fans.

- 'Fight for freedom' -

In Toronto, pro-Hong Kong activists handed out black t-shirts bearing the slogan "The North Stand with Hong Kong" ahead of the Raptors' opener against the Pelicans.

A similar scene unfolded outside the Staples Center in California, where the Lakers and Clippers faced off in their much-anticipated opening game.

Activists said they had produced around 10,000 t-shirts carrying the slogan "Fight for freedom, stand with Hong Kong", which Morey had tweeted.

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A child was seen waving the t-shirt inside the arena before the television camera panned away.

The t-shirt protest in Los Angeles was arranged by an activist who uses the pseudonym Sun Lared, who reportedly raised $43,000 through crowdfunding site GoFundMe to pay for the clothing.

Separately, the flag of Hong Kong was seen being waved behind television pundits outside the Staples Center during the TNT broadcast of the Lakers-Clippers game.

Fans from both Los Angeles teams voiced support for Hong Kong.

"It's always tough to use sports as a political device to talk about, you know, politics," Lakers fan Ray Campbell told AFP.

"But sometimes it's necessary."

Clippers fan Christian Macias added: "Fight for freedom. Stand with Hong Kong. I agree with it 100%, I feel like we are all humans and we all need to help each other."

Earlier Tuesday, NBA legend Shaquille O'Neal said Rockets executive Morey "was right" in his remarks which ignited the furore.

"Daryl Morey was right," O'Neal said. "Whenever you see something wrong going on anywhere in the world, you should have the right to say 'That's not right' and that's what he did."

O'Neal said nothing should inhibit free speech.

"We as American people do a lot of business in China," O'Neal said. "They know and understand our values, and we understand their values."

Lakers star LeBron James sparked controversy last week when he criticized Morey's tweet.

NBA commissioner Adam Silver said last week China had demanded Morey be sacked for his tweet, a claim later denied by Beijing.