Leading government officials in Hong Kong voiced their support on Sunday for the nation's top legislature to introduce a national security law for the special administrative region, saying that it is "constitutional, legitimate and reasonable".

It's "necessary and urgent" for the National People's Congress to enact such a law for Hong Kong, Chief Executive Carrie Lam Cheng Yuet-ngor said on her social media page.

Lam said she has received lots of messages from local residents in recent months. They had asked the government to implement their own national security law, which is part of the SAR's constitutional obligations as stipulated in Article 23 of the Basic Law.

This reflects the widespread concern among most Hong Kong people who are disgusted by violence, separatism and foreign intervention over the past year, said Lam. Since last June, Hong Kong has suffered extensive violence and vandalism caused by anti-government protesters.

Considering the constant delaying tactics of opposition lawmakers, it was very hard to complete local legislation under Article 23, Lam explained.

According to the draft decision, the proposed law will be inserted into Annex III of the Basic Law and take effect through promulgation, instead of local legislation. It will outlaw acts of secession, subversion, terrorism and external interference in Hong Kong.

Lam pledged the government would make the "utmost efforts" to explain the importance of this legislation to local residents.

Chief Secretary for Administration Matthew Cheung Kin-chung said in his blog on Sunday that the city shares the same interests as its motherland. But he noted some people had betrayed the city's fundamental interests. They had incited separatism, localism and extremism that have challenged "one country" over the past year, Cheung added.

These illegal and violent acts, if not effectively contained, can threaten national security, he said.

Cheung said the central government's decision was reasonable considering the legal loopholes in Hong Kong when it comes to safeguarding national security.

Secretary for Justice Teresa Cheng Yeuk-wah also supported the rationale behind the legislation.

"Upholding national sovereignty is the duty of each and every national. When there is no country, there is no home. These are basic principles that any right-minded person will agree on. Vilification of the national security law is utterly irrational," she said.

Secretary for Security John Lee Ka-chiu stressed the need for national security legislation by referring to a recent outbreak of homegrown terrorism which had included the use of explosives.

Lee noted that since last year, Hong Kong has witnessed more than 10 such cases involving explosives and dangerous items. He added that the explosives seized by police, and the aggressive tactics used by radicals, were commonly seen in overseas terrorist attacks.

"Effectively curbing terrorist-like activities that endanger national security will help Hong Kong become a safe and a stable city," said Lee.

Financial Secretary Paul Chan Mo-po also expressed support for the legislation. He said a safe and stable social environment would help business operations and investment activities.

Chan noted that last year's social turbulence had worried investors at home and abroad. It was necessary to legislate the national security law to restore stability in the city, he added.

He also reassured the business sector that their interests would not be affected by the law. "Normal foreign investment and trade activities in the city will continue as usual — as these will not affect national security. There is no need to worry too much," he added.