Lam, in a video message to the Human Rights Council in Geneva, said that legislation to safeguard national security was "urgently needed" for the sake of 7.5 million Hong Kong residents, but also the 1.4 billion people on the mainland.
Hong Kong had been "traumatized by escalating violence fanned by external forces," she said, adding: "No central government could turn a blind eye to such threats to sovereignty and national security as well as risks of subversion of state power."
She noted that the Basic Law - which enshrines the principle of "one country, two systems" to govern Hong Kong after it returned to Chinese rule in 1997 - protects freedoms of speech, assembly and the press.
Hong Kong was rocked by months of sometimes violent anti-China, pro-democracy unrest last year, with protesters angry at perceived meddling by Chinese Communist Party rulers in the city's freedoms.
China denies interference.