The agency is alarmed that children have been sleeping amongst dead bodies, and extremely concerned about the safety of children who have become separated from their families - the quake hit when many children were in school - or whose parents have been killed. There is also growing concern for the safety of twenty staff from Save the Children's Haiti team who remain unaccounted for.
Gareth Owen, Save the Children's director of emergencies, said, "As well as getting basic supplies in, it's crucial that children struggling on their own are protected from being crushed by more debris and are kept safe from abuse on the streets. This is not a safe place for children. We know that the prison has collapsed and lone children are incredibly vulnerable."
Three million people are estimated to have been directly affected, and an average family in the area has at least three children.
Gareth Owen, Save the Children's director of emergencies, said: "This is an unbelievably traumatic experience for children in Haiti. We believe up to two million could be affected, and the emotional damage of what they're going through could last their entire lives.
"Children are petrified and in danger. Many will have been orphaned or be badly injured themselves and in urgent need of medical help. Thousands more will have lost all contact with their families and friends and are now struggling to survive alone in the rubble. They are sleeping on their own, trying to cope with the trauma of seeing dead bodies, and will have no idea where to go for help.
"Children mimic adults in these sorts of crises. They see grown-ups scrabbling through the debris looking for bodies, and will try to follow suit. Aside from the damage this is doing to their mental health, it's putting their safety in danger as buildings will be very unstable and may still collapse."
Gareth Owen continued: "We are also increasingly concerned for the safety of 20 of our team in Haiti, who remain unaccounted for after our offices were damaged in the earthquake."
Save the Children's emergency response teams on the ground are preparing safe spaces for children where they will be properly protected, given space to play and start to get the psychological help they need.
Gareth Owen said: "No generation of Haitian children in a hundred years has experienced this scale of disaster before, and we have to act fast to minimise both the physical and psychological damage to them. Our safe spaces will allow children to start talking about the trauma of what they have seen, to spend time with other children and try to regain some sense of security and calm."
Save the Children has launched a =A33 million emergency appeal for emergency supplies in Haiti. Our team on the ground is already preparing for distributions of food, clean water, shelter and to set up safe spaces to protect children.
To donate to Save the Children's emergency appeal for Haiti call +44 207 012 6400 or go to www.savethechildren.org.uk