Hong Kong's airport has cancelled all remaining departing flights for the second day after protesters took over the terminals.
The airport authority announced early Tuesday evening that check-in services for departing flights were suspended as of 4:30 p.m.
Other departing flights that have completed the process will continue to operate.
The authority advised the public not to come to the airport.
The United Nations' top human rights official has condemned violence in Hong Kong's pro-democracy protests and called on the authorities and protesters to solve their dispute peacefully.
A spokesman for U.N. High Commissioner for Human Rights Michelle Bachelet said she was concerned by the recent "escalation of violence."
The rights office urged Hong Kong authorities to investigate examples of officers firing tear gas canisters into crowded, enclosed areas and directly at individual protesters.
During an emotional press conference Tuesday, Lam said violence carried out during demonstrations risked pushing the Chinese territory to the point of “no return".
Flights at Hong Kong airport have resumed after a massive sit-in there caused major disruptions at the busy international transport hub.
Protesters keep up momentum
However, the widespread unrest – which began 10 weeks ago in response to a proposed extradition bill that has since been shelved – is showing no sign of abating.
Thousands of residents of the former British colony are angry at what they say is an ongoing erosion of freedom and autonomy.
On Monday police unveiled water cannon trucks as a new way to put down protests, which Beijing has described as "terrorism".
Families carrying balloons and banners held a peaceful march through Hong Kong’s financial centre over the weekend, with parents saying the territory was no longer suitable for children.