More than one billion children now live in crowded cities around the world but too many are stuck among the poorest of the poor without electricity, water or education, a UN report said Tuesday.

"Urbanization leaves hundreds of millions of children in cities and towns excluded from vital services," the UN Children's Fund (UNICEF) said.

In a few years, the report said, the majority of children will grow up in towns or cities rather than rural areas. Children born in cities already account for 60 per cent of the increase in urban population.

Cities are growing faster than governments can keep up with and already one in three urban dwellers lives in a slum, The State of the World's Children 2012 report said.

The report said infrastructure and services are not keeping up with urban growth, and poor families often pay more for substandard services. Water can cost 50 times more in poor neighborhoods where it has to be bought from street vendors than it does in wealthier districts linked to mains pipes.

With an urban childhood increasingly becoming the norm, UNICEF said more attention has to be given to children in planning, to get children into schools and protect the tens of millions of children forced into under-age labor and sexual trafficking.

"Hundreds of million of children today live in urban slums, many without access to basic services," said UNICEF executive director Anthony Lake in the report.

"They are vulnerable to dangers ranging from violence and exploitation to the injuries, illnesses and death that result from living in crowded settlements atop hazardous rubbish dumps or alongside railroad tracks," he added.

[Image via]