TikTok said it was addressing online attacks on brands and celebrities, including Paris Hilton and CNN.
However, the video-sharing app told the BBC that a “very limited” number of accounts had been compromised.
It added that it was working with users to restore access to their accounts.
TikTok, owned by Chinese company ByteDance, did not reveal more details about the cyberattack, such as how it was carried out.
A TikTok spokesman said Ms Hilton’s account was hacked but not compromised.
The reality star has more than 10 million followers on TikTok and is an active user of the platform.
However, the account of news broadcaster CNN has been leaked.
“We have been working closely with CNN to restore account access and implement enhanced security measures to protect their accounts,” TikTok said.
“We are committed to maintaining the integrity of our platform and will continue to monitor for any further inauthentic activity.”
CNN did not immediately respond to the BBC’s request for comment.
The news comes as TikTok faces a ban in the United States unless it is sold by its Chinese parent company.
TikTok has millions of users around the world but faces questions about the security of user data and its relationship with the government in Beijing.
It is also becoming the new social media battleground in the US election.
At the beginning of this month, Donald Trump joins TikTokThis despite attempts to ban it on national security grounds during his presidency.
Trump, who has amassed more than 5 million followers since launching his account on Saturday, said he would use “every tool at his disposal to speak directly to the American people.”
President Joe Biden is also using the platform to campaign for re-election in November, but he has only gained about 350,000 followers, far fewer than his rivals.
