At least five children died after taking contaminated measles vaccines in rebel-held areas in the country's northern province of Idlib, the opposition Syrian Observatory for Human Rights said Tuesday.
More than 50 other children got related allergies after receiving the vaccines, Xinhua reported citing the observatory.
The vaccines were provided by the interim "oppositional government", which has been formed in exile but has access to some of the rebel-held areas in the Idlib province.
According to the observatory, 10 others children are believed to have died in the areas of Sinjar, Sheikh Barakeh and Um Moilat in the countryside of Idlib and many more are expected to lose their lives as a result of the deteriorating health situation.
Opposition sources said that the spoiled vaccines may have not been properly stored before being administered to the children.
The opposition forces are in control of considerable portions of Idlib province and the latest incident has cast doubts on the ability of such opposition forces to run the lives of the people under their control.
There have been no remarks from the official Syrian government regarding the incident in Idlib.