TOKYO (REUTERS) - Children under the age of two shouldn't wear masks because they can make breathing difficult and increase the risk of choking, a Japan medical group said, launching an urgent appeal to parents as the country reopens from the coronavirus crisis.

Prime Minister Shinzo Abe lifted a state of emergency for Tokyo and four remaining areas on Monday (May 25) after the number of infections fell across Japan, but warned that it could be reimposed if the virus started spreading again.

To prevent the virus spread, health experts worldwide are recommending people wear masks when it is difficult to maintain social distancing as countries loosen restrictions following coronavirus shutdowns.

But the Japan Pediatric Association has warned parents that masks are too risky for infants.

"Masks can make breathing difficult because infants have narrow air passages", which increases the burden on their hearts, the association said, adding that masks also raise the risk of heat stroke for them.

"Let's stop the use of masks for children under two years old," the association said in a notice on its website.

It said that so far there were very few serious coronavirus cases among children and that most kids became infected from family members, with almost no outbreaks at schools or day care facilities.

The US Centres for Disease Control (CDC) and the American Academy of Paediatrics also say children under the age of two should not wear cloth face coverings.