It's been a bad week for TikTok.

The Chinese-owned video-sharing app, wildly popular with teens, was forced to issue a rare public statement about its data security practices and whether it censors content on behalf of Beijing.

In short, TikTok said it can be trusted with its users' data and that it doesn't delete videos just because of "sensitivities related to China." But that's done little to quiet the app's increasingly vocal critics who worry the platform, with its short lip-sync and comedy videos, is the latest example of Beijing's overseas intelligence-gathering operation.

Toronto-based privacy advocate Ann Cavoukian told CBC News she is skeptical of TikTok's defence, because "surveillance among the Chinese is non-stop."

"I am always wary about statements [saying], 'Oh, trust us,'" said Cavoukian, who is the executive director of the Global Privacy and Security by Design Centre.

TikTok allows users to post seconds-long vertical videos set to music. Most are comedic in tone, ranging from clips of pets in costumes, to teens' impersonations of their parents dancing.

The Beijing-based company ByteDance first released TikTok in 2017 and has since grown it into one of the world's top apps. The company merged TikTok with another popular clip-sharing service, musical.ly, last year.

A recent report by the mobile app data firm Sensor Tower found TikTok to be among the most-downloaded apps worldwide between July and September 2019, second only to messaging software WhatsApp.

Canadian expansion

ByteDance shows signs it's interested in expanding further, particularly in Canada. Ads posted this month on the online professional networking site LinkedIn suggest the firm is seeking to hire staff in Toronto, including a brand partnerships manager and a customer solutions manager .

"We are at the earliest building stages of the global business solutions team in Canada," an online ad for TikTok said. "Today, the market is showing much anticipation and excitement toward this quickly expanding platform."

TikTok did not immediately respond to CBC's request for comment on the firm's Canadian expansion.

Users in Canada are embracing TikTok. As of Friday, it was ranked second among the top-downloaded entertainment programs in Apple's Canadian App Store, above both Netflix and Amazon Prime Video.

A TikTok video of NDP Leader Jagmeet Singh went viral during the recent federal election campaign, as he lip-synced the words "nope" and "yup" from rapper E-40's song Choices, while seeking to highlight his party's platform.

Allegations of censorship

But observers say political videos critical of Beijing have been received less kindly.

Last month, The Guardian reported TikTok takes steps to censor content related to the Tiananmen Square massacre, Tibetan independence or the banned movement Falun Gong — all sensitive topics in China. The report came after the Washington Post highlighted how few TikTok videos out of Hong Kong showed any sign of unrest, even as pro-democracy protests roiled the city.

Mark Zuckerberg, the CEO of rival Facebook, called out the company — and China — in a speech last week.

"While our services, like WhatsApp, are used by protesters and activists everywhere due to strong encryption and privacy protections, on TikTok, the Chinese app growing quickly around the world, mentions of these protests are censored, even here in the U.S.," he said. "Is that the internet we want?"

During a speech this week at Georgetown University in Washington, D.C., Facebook CEO Mark Zuckerberg accused TikTok of censorship. (Nick Wass/The Associated Press)

And earlier this month, U.S. Sen. Marco Rubio accused Beijing of exporting its suppression of free speech with Chinese-developed software, while asking the Committee on Foreign Investment in the United States to look into the company.

"There continues to be ample and growing evidence that TikTok's platform for Western markets … is censoring content that is not in line with the Chinese government and Communist Party directives," Rubio wrote.

In its statement , TikTok shot back at claims of censorship, saying its staff "have never been asked by the Chinese government to remove any content and we would not do so if asked."

TikTok said its American user data is stored in the U.S., with "backup redundancy" in Singapore, and is not subject to Chinese law.

U.S. investigation demanded

The public remarks this week read like a direct response to a letter, released just hours earlier, sent by two other U.S. lawmakers demanding a national security investigation into TikTok.

Democratic Sen. Senator Chuck Schumer and his Republican counterpart Tom Cotton sent the memo to the acting director of national intelligence, alleging TikTok's policies allow the app to collect wide-ranging data from users and that the firm is still required to follow Chinese law.

Experts say Chinese law forces companies to share intelligence with Beijing, even when the data is collected abroad.

Chinese company ByteDance's app TikTok, known locally as Douyin, is seen on display at the International Artificial Products Expo in Hangzhou, China on Oct. 18, 2019. (Reuters)

The concern has been underlined extensively in relation to Huawei, leading the Chinese tech giant to be banned from 5G mobile network development in Australia and Japan.

TikTok, the U.S. senators wrote, is "a potential counter-intelligence threat we cannot ignore."

China is known to have invested heavily in facial recognition technology. And TikTok could potentially act as a source of millions of images of faces, often those of teenagers.

Cavoukian is urging users to delete TikTok — or avoid downloading it in the first place.

"If [your] information is ending up in China, it's the last thing you want, especially at a young age."