Beijing will not allow anyone in Hong Kong to harm national security or use the special administrative region as a base for subverting political and social stability, the government's top liaison official said on New Year's Day.

In an interview with China Central Television, Zhang Xiaoming, director of the Liaison Office of the Central People's Government in Hong Kong, spelled out three lines that should not be crossed.

One must not undermine China's sovereignty over Hong Kong and hurt national security, nor challenge the authority of the central government and Hong Kong's Basic Law, the city's mini-constitution, he said.

The region should also not be used as a base to "infiltrate and subvert" the Chinese mainland, destabilizing social and political order, he added.

The year 2017 marks the 20th anniversary of the establishment of the Hong Kong Special Administrative Region.

Public concern over separatism in Hong Kong grew in 2016 after two lawmakers elected to the city's legislature－Youngspiration's Sixtus Leung Chung-hang and Yau Wai-ching－insulted all Chinese by using foul language and advocating independence during their swearing-in ceremony in October.

Zhang appealed to all people in Hong Kong to strengthen the "sense of the bottom line", uphold the rule of law and stand firm against the rise of separatism.

In turn, authorities and residents from the Chinese mainland should respect and safeguard Hong Kong's sociopolitical system, leaving Hong Kong to handle matters within the scope of its autonomy, he added.

These principles are in accordance with the original intent and fundamental basis of the "one country, two systems" policy, which despite the political discord in recent years, has been "an internationally recognized triumph", he said.

Beijing has adhered to its commitment made before Hong Kong's return to China in 1997, he said, adding that the central government attaches great importance to Hong Kong affairs and will continue its firm support of the city.

Also on Sunday, hundreds of people rallied near the Hong Kong government complex, urging the authority to curb "Hong Kong independence" advocacy through legal and educational means.

Legal professionals and political analysts also joined the demonstration.

Lawrence Ma Yan-kwok, a barrister and chairman of the China-Australia Legal Exchange Foundation, called on the city to operate a "zero tolerance" policy on separatism. He warned that such advocacies would eventually hurt overall interests and limit the freedoms enjoyed by people in Hong Kong.

"The regional government should consider preventing the spread of separatist ideas, and needs to enact its anti-subversion law, to fulfill the requirement stipulated in the Basic Law," he said.

Article 23 of the Basic Law states that the SAR shall enact laws on its own to prohibit any act of treason, secession, sedition, subversion against the central government, or theft of State secrets.