China's cyberspace watchdog announced on Monday that it is examining online recruiter Zhipin.com, as well as truck-hailing apps Huochebang and Yunmanman, as part of a broader crackdown on mainland internet firms in the wake of new data security legislation.

The announcement comes a day after the Chinese Cyberspace Administration (CAC) ordered the suspension of app downloads for Didi Global Inc, a Chinese ride-hailing company that went public in the United States last month.

Last month, Full Truck Alliance, which was formed by the merging of Huochebang and Yunmanman, and Kanzhun Ltd, the owner of Zhipin.com, went public on the New York Stock Exchange.

The CAC stated in a statement that the three app-based enterprises should cease new user registrations while the investigation is underway, adding that the investigations are being conducted to "prevent national data security risks and safeguard national security."

The cyberspace agency did not provide any additional information on the three apps under investigation but did cite China's national security and cybersecurity laws.

Regulators in China have recently increased their scrutiny of online platform businesses, such as Alibaba Group and Meituan, for anti-competitive actions.

The Full Truck Alliance platform, called "Uber for trucks," has over 10 million registered truck drivers and over 5 million truck owners.

According to Kanzhun's prospectus, Zhipin.com, which connects job seekers and companies, is China's largest online recruiter, with 24.9 million monthly active users in the first quarter of 2021.