Urging global action to fight poverty, if not the seemingly unstoppable migration of people from rural areas to cities, the UN housing agency, Habitat, said the growth of slums was a key risk to public health and development.

"The core problem facing the international community is our continuing failure to come to grips with the world's slums," Habitat Chief Anna Tibaijuka said as she opened a week-long meeting of the agency's governing board here.

"Slums, in short, are a toxic mixture of very one of the problems identified in the Millenium Development Goals," she said, adding that "without intervention, the collective slum population will grow to ... three billion people by 2050."

Speaking at Habitat's headquarters in Nairobi -- itself home to the sprawling Kibera ghetto, one of Africa's largest slums with at least 500,000 residents -- Tibaijuka called urban poverty "a slow motion tsunami" deadlier than the giant waves that devastated the Indian Ocean in December.

Such poverty is "much more destructive of lives and livelihoods than all the world's disasters and wars combined," she said.

In a message to the Habitat delegates, UN chief Kofi Annan noted that slum-dwellers in Africa, Asia and Latin America account for some 30 percent of a global urban population now higher than at any point in history.

"Cities hold great potential as engines of growth and social development, yet they are also bastions of inequality in terms of health and living conditions, employment opportunities and the crime and insecurity people routinely face," he said.

The keynote speaker at the conference, Kenyan President Mwai Kibaki, called on rich nations to offer debt relief of reduce rampant poverty in the developing world and slow the growth of slums.

"The international community should implement debt relief, swap debts and debt cancellations, where appropriate, as a means of mobilising resources towards accelating realisation of" development goals, he said.

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