The World Health Organization on Friday recommended that children over 12 should wear masks in the same contexts as adults in the bid to rein in the COVID-19 pandemic.

The UN health agency, in cooperation with UNICEF, published fresh guidance Friday on when it is appropriate for children to wear masks to impede the spread of the coronavirus crisis.

The two UN agencies had convened a group of experts to review the limited data available on children's contribution to the spread of COVID-19, as well as on the benefits of mask-wearing by children.

Based on those findings, as well as considerations surrounding children's developmental needs, they said the advice varied in different age groups.

WHO thus recommends that "children aged 12 and over should wear a mask under the same conditions as adults, in particular when they cannot guarantee at least a one-metre distance from others and there is widespread transmission in the area."

The document acknowledged that much remains unknown about to what degree children contribute to the spread of the novel coronavirus.

But it said that while there is some limited evidence that young children may have lower susceptibility to infection compared to adults, data indicated that teenagers "may play a more active role in transmission than younger children".

The UN agencies said that children under five should not wear a mask.

"This is based on the safety and overall interest of the child and the capacity to appropriately use a mask with minimal assistance," they said.

But they said that in certain circumstances it could be advisable for children between the ages of six and 11 to wear a mask in places where there is widespread transmission of the virus, or in settings where the children were in contact with the elderly or others at high risk of developing serious illness if they contract the virus.

For such young children, though, an adult should be present to supervise that they are using the mask safely, and the potential impact on their learning and development should be taken into consideration. 

According to the new guidance, for children of any age with developmental disorders, disabilities or other specific health conditions that might interfere with mask wearing, "the use of masks should not be mandatory".

It also recommends that children should not be asked to wear masks when playing sports or doing physical activities "so that it doesn’t compromise their breathing", but stresses the importance of keeping a proper distance from others and limiting the number of children playing together.