The number of people hit by deadly floods across West Africa has now topped 600,000, and the heavy rains have also destroyed crops and infrastructure in a region already hard hit by poverty, the United Nations humanitarian arm reported Tuesday.

The rains that began in June have claimed nearly 160 lives, with Sierra Leone, Senegal, Burkina Faso, Ghana and Niger among the countries most affected by flooding, according to the UN Office for the Coordination of Humanitarian Affairs (OCHA).

Roads and buildings have been ruined from Mauritania to Niger, while a key hospital in Ouagadougou, the capital of Burkina Faso, lost medicine and equipment. In the town of Agadez in Niger, almost 400 hectares of vegetable crops and hundreds of livestock were washed away.

"It's a very worrisome situation that further weakens already impoverished populations," said Herve Ludovic de Lys, head of the OCHA in West Africa.

"Natural disasters have lasting consequences that will have an impact for decades to come and take us back to square one in terms of the fight against poverty," he said.

The UN World Food Program (WFP) has started distributing vital food supplies to over 100,000 people in Burkina Faso, Niger and Mauritania.

Adults are being given a 15-day ration of cereals, pulses and vegetable oil, while children receive a monthly supply of food, including sugar and a nutritious corn-soya blend.

"People's lives have been turned upside-down overnight and WFP is moving as swiftly as possible to provide life-saving food assistance," said Josette Sheeran, the agency's executive director. "It is always the poor and vulnerable who suffer most from floods like these as their few remaining assets are swept away, leaving them hungry and destitute."

Many of those in urgent need of help in Ouagadougou, where WFP has already reached 500,000 people since last week, were already receiving the agency's help, but those rations were lost in the floodwaters.

In Niger, WFP started providing supplies Monday to 41,000 people, while it is planning aid distributions to some 12,000 people in Mauritania.

West Africa regularly experiences torrential rainfall during the annual wet season, and the rain can often devastate communities in a matter of hours. In 2007, for example, about 300 people died and 800,000 others were affected.

OCHA noted on Tuesday that climate change is driving these natural disasters, with the region possibly paying a high human cost due to global warming.

Ahead of the UN climate change conference, to be held in Copenhagen, Denmark, when nations are aiming to reach agreement on slashing greenhouse gas emissions, West African nations have been holding frequent high-level and expert meetings on the issue.