Afghanistan's winter could leave up to 100,000 children dead in the next few weeks, according to UNICEF.
Workers are battling to get food supplies and information to Afghans.
UNICEF estimates up to 100,000 Afghan children could die if essential relief supplies are not made available.
Mr Thomas McDermott, of the charity, said: "Winter is approaching fast and we need to move in emergency supplies even quicker in order to help the most vulnerable, the Afghan children and women, to survive these very cold conditions."
Mr McDermott said the relief organisation's priorities in Afghanistan are to conduct an "immunisation program to prevent the spread of epidemic diseases, reactivate social services and getting Afghan children back to school."
Epidemic diseases spreading through Afghan refugee camps near Iran have claimed the lives of hundreds of children in the past few weeks.
Mr McDermott thanked Iran for an "excellent job" in caring for Afghan refugees, who number more than two million.
He said Iran was the source for relief supplies and technical expertise for Afghan refugees.
UNICEF offices in Kabul and Mazar-e-Sharif had restored regular operations and international staff would return to Herat following security checks.
The organisation's offices in Jalalabad and Kandahar remain closed.