Almost 22 million people were forced to flee their homes due to natural disasters last year and the numbers uprooted could increase as urban populations grow, a refugee agency said on Wednesday.

The majority were in Asia, where 19 million were displaced by floods, storms and earthquakes, according to the report from the International Displacement Monitoring Centre (IDMC) of the Norwegian Refugee Council.

Typhoon Haiyan caused the largest displacement, with 4.1 million people leaving their homes in the Philippines, a million more than in Africa, the Americas, Europe and Oceania combined. Typhoon Trami displaced another 1.7 million people in the Philippines and floods in China displaced 1.6 million.

The new statistics show more than twice as many people are affected by natural disasters than 40 years ago and the trend is expected to worsen as more people move to crowded cities in developing countries.

"This increasing trend will continue as more and more people live and work in hazard-prone areas," said Jan Egeland, the Secretary General of the Norwegian Refugee Council. "It is expected to be aggravated in the future by the impacts of climate change."

Africa will be particularly vulnerable as its population is expected to double by 2050.

Last year, seasonal floods caused significant displacements in sub-Saharan Africa, notably in Niger, Chad, Sudan and South Sudan, countries also affected by conflict and drought.

Positive trends include improvements in disaster preparedness and response measures, including early warning systems and emergency evacuations, which mean that more people now survive disasters. Improved data collection helps planning for future catastrophes.

"Most disasters are as much man-made as they are natural," said Alfredo Zamudio, IDMC's director. "Better urban planning, flood defenses and building standards could mitigate much of their impact."