"The United States stands with the people of Hong Kong," said US Treasury Secretary Steven Mnuchin.

The sanction by the US Treasury comes weeks after China imposed the new National Security Law in Hong Kong, curbing freedom that were otherwise enjoyed by Hongkongers.

The United States accused Lam of "implementing Beijing's policies of suppression of freedom and democratic processes".

In 2019, Lam pushed for an update to Hong Kong's extradition arrangements to allow for extradition to the mainland, setting off a series of massive opposition demonstrations in Hong Kong," the Treasury statement read.

The law gives Beijing a free hand to carry out trials of 'potential suspects' on the Chinese mainland. It also allows officials to carry out close door trials and designate those damaging public facilities- like transport- terrorists.

Experts believe the law will curb online freedom and make user data public as companies will be forced to share information if and when requested by law enforcement officials.

Several legal experts have also pointed at the ambiguous wordings in the law, that make it difficult for citizens to fully comprehend what constitutes a criminal offence and what is exempted from it.

According to the law, the trials can be a secret affair(Article 41) and can be held without a jury (Article 46).

Article 44 also states that the judges can be handpicked by Hong Kong's chief executive, who is answerable directly to the mainland.

Meanwhile, the US move has been termed "blatant and barbaric interference of the internal affairs of the People's Republic of China".

Lam's spokesperson said she would not be 'intimidated' by the US sanction.

Speaking on behalf of her senior colleagues who are being targeted, the Chief Executive Mrs Carrie Lam said that we are discharging an honourable duty to safeguard national security, protecting the life and interests of not only the 7.5 million Hong Kong people but also the 1.4 billion Mainlanders," the spokesperson said.

Following the sanctions, those named, will have their properties in the US seized and financial assets frozen by authorities.

"The Chinese Communist Party has made clear that Hong Kong will never again enjoy the high degree of autonomy that Beijing itself promised to the Hong Kong people and the United Kingdom for 50 years," said US Secretary of State Mike Pompeo while announcing the sanctions on Friday.

President Trump has made clear that the United States will therefore treat Hong Kong as 'one country, one system' and take action against individuals who have crushed the Hong Kong people's freedoms," Pompeo added.

Reacting to China's move, the US in July decided to scrap the preferential economic treatment given to Hong Kong after Beijing imposed a new national security law in the region.

US President Donald Trump signed an order along with a bipartisan legislation to impose sanctions on Chinese officials violating human rights law in the territory.

"Hong Kong will now be treated the same as mainland China," the US President was quoted as saying in the media.

"No special privileges, no special economic treatment and no export of sensitive technologies," he told reporters.

According to Trump, the Hong Kong Autonomy Act, which he signed and was passed unanimously in the US Congress earlier in July, will give the President 'powerful new tools to hold responsible the individuals and the entities involved in extinguishing Hong Kong's freedom'.

Apart from Lam, the US has sanctioned the former and current commissioners of the Hong Kong Police Force, Stephen Lo and Chris Tang, respectively.

Justice Secretary Teresa Cheng and Security Secretary John Lee; Beijing's representative in Hong Kong, Luo Huining, are among those sanctioned by the Trump administration.

Hong Kong has vowed retaliation.

Hong Kong Commerce Secretary Edward Yau has said US businesses in the region could face sanctions.