Social media site TikTok has apologised for removing a video that hid messages about Chinese treatment of Muslims, and attempted to explain how it was removed.

The post appeared to be a makeup tutorial but actually included references to Uighurs in China, and suggestions of how people could learn more about the actions of the Chinese government.

But soon after it was posted it was removed, in a decision that led many to fear that TikTok – which is owned by Chinese company ByteDance – was engaging in censorship on behalf of China's government.

Now the social media company said that the video was restored within an hour and that it had only been taken down because of a "human moderation error".

The controversy over the video, viewed 1.6 million times, comes as TikTok's Chinese owner, ByteDance, faces an inquiry by a U.S. national security panel over its handling of personal data, while U.S. lawmakers fear it may be censoring politically sensitive content.

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In the video she posted last week, the user, who identifies herself as Feroza Aziz, gave a tutorial on eyelash curling, while talking about how Muslims were being treated, and saying she wanted to spread awareness of the situation.

But on Twitter this week she said she had been blocked from posting on TikTok for a month, and on Wednesday posted that her viral video had been taken down, only to be restored later.

The video was offline for 50 minutes, TikTok said on its website.

"We would like to apologise to the user for the error on our part," said Eric Han, the app's U.S. head of safety.

"Due to a human moderation error, the viral video from Nov. 23 was removed. It's important to clarify that nothing in our community guidelines precludes content such as this video, and it should not have been removed."

The TikTok user did not immediately respond to requests from Reuters for additional comment.

China's foreign ministry said it had no specifics of the case, when queried by Reuters about the incident on Wednesday.

But it added that it required Chinese firms to operate in a way that respected international norms and local laws and regulations, and hoped that relevant countries also provided a fair and non-discriminatory environment.

TikTok is not available in China, but ByteDance has a domestic version called Douyin.

The user did not mention Uighurs in the video, but said later on Twitter she had been referring to the minority ethnic group.

United Nations experts and rights groups estimate more than a million Uighurs and members of other ethnic groups have been detained in camps in China's far western region of Xinjiang, which has triggered international condemnation.

China says the camps are re-education and training centres.

ByteDance has stepped up efforts to ring-fence TikTok, popular with U.S. teenagers and those in their 20s, from much of its Chinese operations, Reuters reported on Thursday.

In a timeline on its blog post, TikTok said it had blocked another account set up by Aziz that had posted an image of Osama Bin Laden which violated its content policies regarding "terrorist imagery".

On Monday, it enforced a device ban on accounts associated with violations. This affected the new account from which Aziz had posted the eyelash curling video and sent from the same device, it said.

It said it had decided to override the device ban and was directly contacting her to do so.

Aziz confirmed on Twitter that TikTok had restored her account but said other past videos had been deleted.

"Do I believe they took it away because of a unrelated satirical video that was deleted on a previous deleted account of mine? Right after I finished posting a three-part video about the Uyghurs? No," she posted on Twitter.