The UN health agency on Tuesday confirmed an outbreak of polio in war-torn Syria, which had been free of the crippling disease since 1999, and said it feared it would spread.
Oliver Rosenbauer, spokesman for the World Health Organization's anti-polio division, told reporters that laboratory tests had confirmed the presence of the disease in 10 out of 22 suspected cases reported almost two weeks ago.
All 22 children were stricken with acute flaccid paralysis, which is the symptom of a number of different diseases, including polio.
"Out 10 of those cases, they've isolated wild polio virus type one," Rosenbauer said.
"The other 12 are still being investigated," he added, saying test results were expected in coming days.
The cases were clustered in the northeastern Deir Al Zour province, and all affected children under the age of two.
"There are no additional 'hot' cases that we know of. Of course disease surveillance is now ongoing across Syria and neighbouring countries as well, to look for other acute flaccid paralysis cases," said Rosenbauer.
The next step is to analyse the genetic code of the virus to try to track its source.
"This is a communicable disease, and with population movements it can travel to other areas, and so the risk is high of a spread across the region of course," Rosenbauer warned.
Last week, as they waited for confirmation of the cases, aid agencies and Syrian health authorities stepped up efforts to vaccinate 2.4 million children against polio, as well as measles, mumps and rubella.
The UN says that 500,000 children in Syria have not been vaccinated against polio in the past two years due to insecurity.
Before the Syria conflict, around 95 percent of all Syrian children were vaccinated.
Rosenbauer said that all the children who have caught the virus in Deir Al Zour appeared to have never been vaccinated against polio, or had not received a full course of vaccine.
Some 115,000 people have been killed in Syria and millions driven from their homes since a brutal crackdown on Arab Spring-inspired protests in March 2011 escalated into civil war.