The World Health Organization said Friday that Covid-19 tests should be carried out in schools in some circumstances to avoid the "harmful" effects of closures and remote learning.

"The summer months offer a valuable window of opportunity for governments to put in place the right set of measures that will help keep infection rates down and avoid resorting to school closures," Hans Kluge, WHO's regional director for Europe, said in a statement issued together with UNICEF and UNESCO.

He added that closing schools "as we have seen, have such a harmful effect on the education, social and mental well-being of our children and youth."

"We can't allow the pandemic to rob children of their education and development," said Kluge, who has repeatedly called for countries in the WHO's European Region to address dropout rates and health effects linked to distance learning.

According to the new recommendations published on Friday, testing should be prioritised for symptomatic children with acute respiratory infection "of any severity" if they belong to a vulnerable group.

Also asymptomatic close contacts of Covid cases should be considered for testing, the WHO said.

However testing is not recommended if no coronavirus cases have been detected in a school, the WHO said.

The WHO's European Region spans 53 countries and territories and includes several in Central Asia.

For the UN agencies, closing schools "should be considered only as a measure of last resort", when there is an explosion of cases which cannot be controlled by other measures.