China passed a law Thursday tightening controls over foreign non-governmental organizations by subjecting them to close police supervision, a move officials say will help the groups but critics charge is the latest attempt by authorities to clamp down on perceived threats to the ruling Communist Party's control.

The law, adopted by the national legislature, states that foreign NGOs must not endanger China's national security and ethnic unity. It grants police the power to question NGO administrators, search residences and facilities and seize files and equipment.

The move to pass such a law has drawn criticism from U.S. and European officials and business and academic organizations. They are concerned it will severely restrict the operations of a wide range of groups, further limiting the growth of civil society in China and hindering exchanges between China and the rest of the world.

The law includes a clause that allows police to blacklist "unwelcome" groups and prevent them from operating in the country. Groups can be blacklisted if they commit violations ranging from illegally obtaining unspecified state secrets to "spreading rumors, slandering or otherwise expressing or disseminating harmful information that endangers state security."

The Network of Chinese Human Rights Defenders denounced the law as "draconian," saying it allows police to exercise "daily supervision and monitoring" of foreign NGOs. The law will have "a profoundly detrimental impact on civil society in China," it said.

The group said the most alarming aspects include the ability of police to end foreign NGO-organized activities that they deem to "endanger national security," a term that is not clearly defined. Police will also be able to more closely monitor foreign organizations' funding sources and expenses, "which has the chilling effect of intimidation," the group said.

The law appears to be an effort to utilize of the resources and expertise of foreign NGOs as China struggles with problems including environmental pollution and mental health, while preventing them from competing with the Communist Party for hearts and minds.

Still, the final version of the law eased many of the restrictions included in an earlier draft, including exempting foreign schools, medical facilities, and academic and research groups in natural sciences and engineering technology.

It also allows foreign NGOs to set up multiple representative offices in China, removes restrictions on hiring volunteers and staff, and eliminates a requirement that they reapply for permission to operate in China every five years.

However, in an apparent attempt to limit their influence, the law bans foreign groups from setting up regional chapters, recruiting members from among the public at large or raising funds within China. It also subjects them to closer financial scrutiny, requiring that they submit annual reports detailing their sources of financing, spending activities and changes in personnel.

"You are here to do deeds, not to build up your troops," Guo Linmao, a legal inspector for the legislature, said at a news conference following the law's passage.

Guo sought to offer words of assurance, saying the law aims primarily to welcome foreign non-governmental groups, help promote their activities and protect their lawful interests while filtering out those few organizations that may hurt China's national security and interests in the name of NGO work.

And, despite a relentless crackdown on domestic legal aid and civic society groups, Guo said international organizations working on human rights issues are welcome in China, as long as they comply with Chinese laws.

He said the law shifted the authority to register and supervise foreign groups from civil affairs bureaus to the police in part because Chinese police already have responsibility for managing and overseeing foreign nationals.

Many overseas organizations have partnered with Chinese academic and social groups, but still operate in a legal gray area that leaves them vulnerable to crackdowns by security forces.

In one recent example, China in January deported a Swedish man it accused of training and funding unlicensed lawyers in the country.