Chief Secretary Eric Chan said on Saturday that Washington is pulling out all the stops to suppress the nation's development through Hong Kong, adding that the US government's plan to intimidate investors coming to the SAR will not succeed.

In a joint release, the US Departments of State, Agriculture, Commerce, Homeland Security, and Treasury said overnight on Saturday that firms operating in Hong Kong are facing "increasing risks" that it said stem from national security laws in the SAR.

The city's number two official said people should remain cautious, given that the US will likely continue to make excuses to suppress Hong Kong.

Speaking to reporters, Mr Chan said that US' national security policies are stricter than those in the SAR, and with more severe punishment.

"Why do they have to target Hong Kong? Our national security law has been legislated for so long, I believe everyone can see whether we have falsely accused or arrested any businessmen, or arrested anyone without evidence. There's no such thing," he said.

"In many national security cases in the past, all evidence is presented in court for both the prosecution and defense to look into. In the end, our courts will decide fairly and independently whether the defendants are guilty or not."

Constitutional and mainland affairs minister Erick Tsang also hit out at the advisory, calling the claims "fictitious" and factually wrong.

Speaking on Commercial Radio, Tsang responded that the advisory was just more of the 'usual tricks' used by western countries as part of their smear campaign against Hong Kong.

"We've always said that no matter if it's the national security law, or the Safeguarding National Security Ordinance under Article 23 of the Basic Law, these are stablisers for Hong Kong. 'A pillar of the ocean'," he said.

"We have repeatedly stressed that Hong Kong's freedoms, be it free speech or other freedoms, are protected by law. These so-called warnings or dangers, if you ask me, are deliberate attempts to suppress our country's development, as well as Hong Kong's."