GENEVA: The number of registered child refugees fleeing Syria's violence has topped the one million mark in another grim milestone of the deepening conflict, two UN agencies said Friday.

Roughly half of all the nearly two million registered refugees from Syria are children, and some 740,000 of those are under the age of 11, according to the UN refugee and children's agencies.

''This one millionth child refugee is not just another number,'' said Anthony Lake, the head of UNICEF, the UN children's agency. ''This is a real child ripped from home, maybe even from a family, facing horrors we can only begin to comprehend.''

The children's ordeals are not over once they escape Syria, said Antonio Guterres, the head of the Office for the UN High Commissioner for Refugees, known as UNHCR.

''Even after they have crossed a border to safety, they are traumatized, depressed and in need of a reason for hope,'' he said.

His agency said it tries to ensure that babies born in exile are provided with birth certificates, preventing them from becoming stateless, and that all refugee families and children live in some form of safe shelter.

But the threats to refugee children are rising, the agencies say, including child labor, early marriage and the potential for sexual exploitation and trafficking.

More than 3,500 children in Jordan, Lebanon and Iraq have crossed Syria's borders unaccompanied or separated from their families, according to the UN figures.

The agencies say some 7,000 children are among the more than 100,000 killed in the unrest in Syria, which began in March 2011 and later exploded into a civil war.

Most of the refugees fleeing Syria have arrived in Lebanon, Jordan, Turkey, Iraq and Egypt. However, UN officials say that increasingly Syrians are fleeing to North Africa and Europe.

The two UN agencies estimate that more than two million children also have been displaced within Syria.