The World Health Organization (WHO) said it has officially asked China for detailed information about a concerning spike in respiratory illnesses and clusters of pneumonia in children in parts of the country.

Chinese authorities from the National Health Commission earlier this month reported an increase in respiratory diseases in China, attributing the rise to the lifting of COVID-19 restrictions and the spread of the flu and other respiratory viruses, WHO said Wednesday.

The U.N. health agency cited unspecified media reports and a global infectious disease monitoring service as reporting clusters of undiagnosed pneumonia in children in northern China, though said it was unclear whether those were linked to a rise in respiratory infections reported by Chinese authorities.

Scientists outside of China said the circumstances should be monitored but were not concerned that the surge was a sign of a new global outbreak.

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People wearing face masks walk in Beijing

The World Health Organization says it has made an official request to China for information about a potentially worrying spike in respiratory illnesses and clusters of pneumonia in children. (AP Photo/Andy Wong, File)

WHO has advised the people in China to follow measures to reduce the spread of such illnesses, including vaccination, keeping distance from those who are ill, staying home when ill and wearing masks when appropriate.

Residents wearing face masks

Residents wearing masks walk past an advertisement outside a mall in Beijing on Tuesday. (AP Photo/Ng Han Guan, File)

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China’s National Health Commission, in a written Q&A posted online by the official Xinhua News Agency, suggested Thursday that children with mild symptoms "first visit primary healthcare institutions or pediatrics departments of general hospitals" because large hospitals are crowded and have long waiting times.

Residents wearing face masks

China's National Health Commission suggests that children with "mild symptoms" visit primary care doctors. (AP Photo/Andy Wong, File)

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The health commission said it has been paying close attention to the high incidence of infectious diseases among children and is "guiding local authorities to enhance coordinated scheduling and implement a tiered diagnosis and treatment system."

The Associated Press contributed to this report.