People in areas of suspected high Covid-19 transmission should wear non-medical masks in indoor spaces including workplaces and schools, according to new World Health Organisation (WHO) advice.
The updated guidance published on Wednesday also recommends the use of face coverings at home when receiving visitors if one-metre distancing cannot be maintained or ventilation is poor.
The advice issued by the UN agency comes despite "limited evidence" of the effectiveness of mask wearing by the public in the community.
In areas with known or suspected spread of Covid-19, the WHO recommends people should wear a mask indoors and outdoors where distancing of at least one metre cannot be maintained.
The advice, which applies to shops, schools and shared workplaces, also states masks should be worn indoors regardless of social distancing unless ventilation has been assessed to be adequate.
People should also wear a mask at home when receiving visitors if they cannot maintain distancing or ventilation is poor, the WHO recommends.
Children aged up to five should not wear masks, a "risk-based approach" should be taken for six to 11-year-olds, while those aged 12 and over should follow the same principles as adults, the guidance states.
It also says masks should not be worn during vigorous physical activity.
The WHO said its Covid-19 Guidance Development Group (GDG) "considered all available evidence on the use of masks by the general public including effectiveness, level of certainty and other potential benefits and harms, with respect to transmission scenarios, indoor versus outdoor settings, physical distancing and ventilation".
The recommendations were made "despite the limited evidence of protective efficacy of mask wearing in community settings".