The United Nations human rights office said on Friday that any new government measures to cope with protests in Hong Kong must be grounded in law and protect the right to freedom of assembly.
Any use of force should be exceptional and only in compliance with international standards, including the principles of necessity and proportionality, U.N. human rights spokeswoman Marta Hurtado told a Geneva briefing.
Hong Kong's embattled leader Carrie Lam invoked colonial-era emergency powers on Friday for the first time in more than 50 years, in a dramatic move intended to quell escalating violence in the Chinese-ruled city.
Lam said a ban on face masks would take effect on Saturday under the emergency laws that allow authorities to "make any regulations whatsoever" in whatever they deem to be in the public interest.
Hurtado, asked about the measures, said: "Any restriction must have a basis in law and be proportionate and as least intrusive as possible. Freedom of peaceful assembly is a fundamental right and should be enjoyed without restriction to the greatest extent possible."
The use of firearms was only acceptable as a "last resort", and only to protect against an immediate threat, she added.