BEIJING, July 5 - China's cyberspace watchdog said Monday that it is investigating online recruiter Zhipin.com, and truck-hailing apps Huochebang and Yunmanman, ramping up a crackdown on tech companies amid tightened regulations on data security.

The announcement comes a day after the China Cyberspace Administration (CAC) ordered it to suspend app downloads for Chinese ride-hailing giant Didi Global Inc (DIDI.N), which went public in a U.S. listing last month.

Full Truck Alliance (YMM.N), the result of a merger between Huochebang and Yunmanman, and Kanzhun Ltd (BZ.O), owner of Zhipin.com, went public on the US stock market last month.

The CAC said in a statement that the three app-based companies must stop registering new users during the review, adding that the investigations are aimed at "preventing national data security risks and safeguarding national security."

The cyberspace agency did not provide further details on the investigation of the three apps but cited China's National Security Law and cybersecurity law.

Chinese regulators have also recently tightened scrutiny of internet platform companies, including Alibaba Group (9988.HK) and Meituan (3690.HK), for anti-competitive practices.

The Full Truck Alliance, often dubbed "Uber for Trucks," has more than 10 million registered truck drivers and more than 5 million truck owners on its platform.

Zhipin.com, which connects job seekers and employers, is China's largest online recruitment company with 24.9 million monthly active users in the first quarter of 2021, Kanzhun said in the prospectus.

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