Taiwan has launched a probe into an allegedly illegal subsidiary set up by TikTok on the island as it warned the Chinese-owned social media app was a security risk.

The Mainland Affairs Council, Taiwan's top China policy-making body, said the cabinet had requested a multi-agency investigation during a meeting on security issues posed by TikTok earlier this month.

The "illegal operations" case was also forwarded to prosecutors for investigation after a local company allegedly engaged in business activities in Taiwan on behalf of ByteDance, TikTok's Chinese parent firm, MAC said without elaborating.

"In recent years, China has used TikTok and other short videos to conduct cognitive operations to infiltrate other countries," MAC said in a statement issued late Sunday.

"There is also a high risk of users' personal information being collected for the Chinese government."

China's authoritarian Communist Party claims democratic and self-ruled Taiwan, and has vowed to one day seize it.

Relations between Beijing and Taipei are at their worst in years.

Chinese internet and social media platforms are currently banned from operating businesses in Taiwan under local laws.

TikTok is available in Taiwan but is not especially popular.

Local newspaper Liberty Times reported on Monday that the subsidiary under investigation was a company set up in 2018 that changed its name to ByteDance Taiwan Ltd Co in November.

TikTok has come under increasing pressure, especially in the United States, over its Chinese ownership and whether it poses a national security threat.

US senators last week voted unanimously to ban the video-sharing app on government phones, part of a growing bipartisan crackdown on TikTok.

TikTok itself denies being a security risk or beholden to Chinese authorities.

Taiwan has long warned that it is on the receiving end of huge Chinese disinformation and espionage campaigns.

It has ramped up scrutiny of Chinese businesses in recent years and imposed investment rules on various key sectors, including the island's state-of-the-art semiconductor industry.

Beijing has increased military, diplomatic, and economic pressure on the island since Tsai Ing-wen became Taiwan's president in 2016, as she views the island as a sovereign nation and not part of "one China".

Taipei has also accused Beijing of stepping up so-called "grey zone" threats, from warplane incursions into its air defense zone to cyberattacks and cognitive warfare.