The UN's disaster chief has outlined a 10-year plan of investment to avert a natural disaster that could be 100 times worse than the Asian tsunami.
The tsunami tragedy has been a "global eye opener"
Jan Egeland proposed diverting 10% of what is currently spent on emergency relief to tackle disaster prevention.
He told a conference in Kobe, Japan, that action needed to be taken to prevent a "megadisaster in a megacity".
If that happened, the casualty rate could be 100 times worse than that of December's tsunami, he warned.
Mr Egeland, the UN 's director of disaster relief, described as "perhaps the most frightening prospect" a natural disaster in a city with a population of 10 million or more.
He said many cities, including Tokyo, were extremely vulnerable to natural disasters. Poorer cities were most at risk because of a lack of investment and planning.
"Then we could have not only a tsunami-style casualty rate as we have seen late last year, but we could see 100 times that in a worst case," he told the international conference on natural disasters.
'Momentum of understanding'
He said December's tsunami, which has claimed more than 160,000 lives in 12 countries, had been a "global eye opener to the devastating impact of natural disasters".
He added: "We have a momentum of understanding, and we have to use that as much as we can to get institutions going and get funds, not only for relief but also for early warning, for prevention and development."
In 2002, 300 million people were affected by drought in India, and millions more by similar problems in Ethiopia and Zimbabwe. Flooding in China affected 190 million.
Mr Egeland urged the 3,000 delegates to adopt a "proposed framework of action".
"I would propose that over the next 10 years, a minimum of 10% of the large sums now spent on emergency relief by all nations should be earmarked for disaster reduction," he said.
He said there needed to be better city planning, more development and investment in poorer areas.
The five-day conference was originally organised as a meeting of scientists before December's earthquake off Indonesia and the devastating waves it triggered.
It coincides with the 10th anniversary of the earthquake that ravaged Kobe and killed more than 6,500 people.