The purpose of formulating the national security law for Hong Kong is not to take the pro-democracy camp in the special administrative region as an "imaginary enemy", but targeting the narrow category of crimes against the national security, Zhang Xiaoming, deputy director of the State Council's Hong Kong and Macao Affairs Office, said.

"The local society of Hong Kong is diverse and the local politics is diverse. The 'one country, two systems' principle has demonstrated the political tolerance of the central government," Zhang told a news conference in Beijing on Wednesday.

"Various parties including people with different political views and different positions will continue to exist for a long time in Hong Kong."

The Standing Committee of the National People's Congress, China's top legislature, unanimously passed a national security law for Hong Kong on Tuesday, prohibiting acts of secession, subversion, terrorism and collusion with foreign or external forces that endanger national security.

The law was added to Annex III of the Basic Law and took effect later on Tuesday.

Responding to the allegation that enactment of the national security law is to disqualify people from the opposition camp in the upcoming Legislative Council election in September, Zhang said this view is "narrow-minded".

"The purpose of the central government to formulate this law is to safeguard national security, restore stability in Hong Kong and promote long-term implementation of the 'one country, two systems' principle," he said.