The United States on Friday warned its business community of growing risks of operating in Hong Kong following a clampdown by China in the major financial hub.

In a long-awaited advisory that has already been denounced by China, US government agencies led by the State Department told entrepreneurs that they face particular risks from the imposition a year ago of a draconian new security law.

The advisory said there were "growing risks" that "could adversely affect businesses and individuals operating in Hong Kong."

"As a result of these changes, they should be aware of potential reputational, regulatory, financial and, in certain instances, legal risks associated with their Hong Kong operations," it said.

The advisory acknowledged that Hong Kong, a former British colony handed back to China in 1997, "retains many economic distinctions" from the mainland including stronger protections of intellectual property.

The United States is warning of growing risks to businesses in Hong Kong, seen in May 2021
The United States is warning of growing risks to businesses in Hong Kong, seen in May 2021 AFP / Peter PARKS

But it pointed to a changing climate under the national security law including the arrest of one US citizen -- John Clancey, a prominent human rights lawyer.

Dozens of people have been charged under the law, which bans subversion and other offenses against the state, including the media tycoon Jimmy Lai, former lawmakers and pro-democracy activists.

The US advisory also warned of heightened risks to data privacy and a lack of transparency and access to information, noting the closure of a leading newspaper, Apple Daily, which was a thorn in the side of authorities.

It noted as well that businesses were at greater risk of incurring US sanctions, which have been implemented in response to rights concerns.

China imposed the security law in June 2020 after massive and sometimes destructive protests that demanded the preservation of fundamental rights promised to the city before the handover.