The head of the Hong Kong and Macau Affairs Office is not ruling out demonstrations when he said there were other ways to express one's views, a political heavyweight said on Saturday.

In a half-hour address marking National Security Education Day, Beijing's top official overseeing SAR affairs, Xia Baolong, said maintaining national security is not contradictory to expressing interests, adding that demonstrations are not the only way for people to say what they want.

Basic Law Committee vice-chairwoman Maria Tam said freedom of procession and the right to demonstrate are fully protected by the Basic Law.

"When necessary, reasonable and necessary restrictions could be imposed with regard to safety, public order and national security," she said.

Asked if Xia's remarks meant Hong Kong people should not take part in rallies in future, Tam said: "I don't think what he said carried this meaning."

A local deputy to the National People's Congress, Brave Chan, noted that some groups had successfully held demonstrations that met legal requirements.

"We could see that there are always different groups gathering outside the government headquarters and the Legislative Council to voice their demands. This meant their rights and interests continued to be protected in accordance with the law," Chan said.

Executive Council convenor Regina Ip, for her part, said demonstrations in Hong Kong must be regulated, after going through what she said was a "painful experience" in 2019 when peaceful protests turned violent.

"I don't see any problem with [protesters having to] wear a name tag, I am wearing one today," she said.