The Hong Kong authorities formally banned the "Hong Kong National Party (HKNP)" on Monday, the first separatist party in the city since its return to the Chinese mainland in 1997.

Lee Ka Chiu, secretary for the security of the Hong Kong Special Administrative Region (HKSAR) ordered the ban on Monday and it would take into effect upon publication of the government gazette.

"In exercise of the power conferred on the Secretary for Security by Section 8(2) of the Societies Ordinance, I hereby order that the operation or continued operation of the Hong Kong National Party in Hong Kong to be prohibited," said the notice under Lee's name.

The Hong Kong and Macao Affairs Office of the State Council said Monday it resolutely supports the HKSAR's ban on the "Hong Kong National Party."

The spokesperson of the office added that the HKNP is an unregistered and illegal group, as well as a "Hong Kong independence" organization.

The HKSAR government's decision to bar the group from operating according to relevant laws and legal procedures is an action that should be taken to maintain national security and the rule of law in Hong Kong, and is absolutely necessary, the spokesperson said. "We resolutely support the decision."

The central government firmly supports the HKSAR in punishing any acts that jeopardize national security under the law and has zero tolerance for any organizations preaching "Hong Kong independence" or engaging in activities that intend to split the country, he stressed.

The "Hong Kong National Party" was established in March 2016.

(With inputs from Xinhua)