Seventeen children have been paralysed by polio following an outbreak of the disease in Syria that the World Health Organization says is “very serious”.

Earlier this month, the agency reported two polio cases in the Mayadin area of Deir al-Zour province, much of which is controlled by so-called Islamic State.

Fourteen new cases have now been confirmed in the same area, while another was recorded in Raqqa province.

It is the first re-emergence of polio in the war-torn country since 2014.

The highly infectious disease, caused by a virus, mainly affects children under five years of age.

One in 200 infections leads to irreversible paralysis. Among those paralysed, 5-10% die when their breathing muscles become immobilised.