Of the 21 million people affected by the massive floods in Pakistan, 3 million are children under the age of 5, the aid agency says. Because the children are exposed to contaminated water and other elements in tent camps now substituting as home, they are vulnerable to disease, particularly after enduring seven weeks without adequate food and medical care.
At least 12,000 children have become acutely malnourished since the onslaught of the floods late July. But experts say that number could be 10 to 15 percent higher as children in the most remote areas slip through the net.
"The numbers of malnourished and critically sick children will rise dramatically in October and November as the food crisis takes its toll," said Save the Children's country director in Pakistan Mohammed Qazilbash in a release.
"These children have weakened immune systems because of the shortage of food, making them very vulnerable to disease," he said.
More than 10 million people will be in need of food until at least the end of January, estimates from the U.N. World Food Program indicate.
Qazilbash said: "Pakistan's children urgently need more support to survive and rebuild their lives. We need money for clinics, to rebuild schools and to help people begin to farm again and provide food for their families. This is not something that is going to go away. We have to act now before it is too late."
Save the Children's warning comes as the United Nations launched on Friday the largest ever natural disaster appeal -- for more than $2 billion -- to provide aid to those affected by the floods.
The $2 billion includes an August U.N. appeal of $459 million, which is 80 percent funded but still leaves a shortfall of about $1.6 billion, the United Nations says.
The floods have damaged or destroyed nearly 1.9 million homes and have devastated at least 62,000 square miles, an area larger than England.
In announcing the appeal for Pakistan, U.N. Secretary-General Ban Ki-moon said it is the worst natural disaster the organization has responded to in its 65-year history.
The $2 million will provide aid for up to 14 million people over a 12-month period.
In appealing for the additional aid for Pakistan, U.N. Undersecretary-General for Humanitarian Affairs and Emergency Relief Coordinator Valerie Amos said, "We simply cannot stand by and watch the immense suffering in a disaster of this scale."
Notable deaths of 2014 [PHOTOS]