Humanitarian agencies said Thursday that they need $1.2 billion in critical aid for seven drought-stricken countries in southern Africa, as the El Nino weather phenomenon continues to devastate crops across the region.

An estimated 12.3 people million are at risk, southern Africa's Regional Inter-Agency Standing Committee said, as their food stocks are exhausted and their access to safe drinking water becomes limited.

The hardest hit countries are Angola, Lesotho, Madagascar, Malawi, Mozambique, Swaziland and Zimbabwe.

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) warned that if the agencies failed to raise the funds in time, the consequences of the drought would be catastrophic.

"Droughts, like the one caused this year by El Nino, are becoming more frequent and more severe," said Timo Pakkala, OCHA El Nino Coordinator for Southern Africa.

"The time to act is now... not only only to save lives now, but also to prevent crises of this scale happening again."

The drought has been labelled the worst in 35 years.

Zimbabwe, Malawi and Mozambique have all issued drought alerts in recent months, as thousands of cattle die, reservoirs shrink and harvests fail.

Pakkala said the situation had been worsened by the timing of the drought, which hit as the economies of many of the affected countries were struggling.

"We are at a critical point," said CARE regional director Emma Naylor-Ngugi.

"People are being pushed to the brink... unless donors provide more funding, millions of people will suffer and hard-won development gains will be reversed."

The agencies said it was vital to scale up their response to prevent hunger-related deaths.

"I hope we will not get to that point," said Lewis Hove, from the Food and Agriculture Organisation.

"We are working to make sure that it does not happen."