The World Health Organization said it has confirmed two new cases of polio in Syria.
An outbreak of 15 cases was found in northeastern Syria last month, prompting the largest-ever polio immunization campaign in the region.
The U.N. health agency said Tuesday the virus has now infected a child in rural Damascus and another in the northern city of Aleppo.
The polio outbreak is the first in Syria since 1999. The WHO has warned of the high risk of the virus spreading because of large population movements in response to the country's ongoing crisis.
The agency is working to vaccinate 20 million children in seven countries and territories in an operation it expects to continue for at least six to eight months.