Food emergencies in Africa are occurring three times more often now than in the mid-1980s, but the global response to famine continues to be "too little, too late", the international aid agency Oxfam said on Monday.

Conflict, AIDS and climate change are all exacerbating food shortages for sub-Saharan Africa's 750 million people, with innovative solutions and massive long-term support needed to break the cycle, the British-based group added in a new report.

"It will cost the world far less to make a major investment now in tackling root causes of hunger than continuing the current cycle of too little, too late that has been the reality of famine relief in Africa for nearly half a century," Oxfam Britain's director Barbara Stocking said.

Billions of dollars of aid have been pumped into sub-Saharan Africa in recent decades, and its problems have received unprecedented international attention of late from grassroots campaigners and world leaders like Britain's Tony Blair.

But despite that, a "myopic, short-term" focus has prevailed, with emergency food aid still dominating international action on Africa, rather than long-term support of agriculture, infrastructure and social safety nets, Oxfam said.

It cited this year's drought in east Africa, where up to 11 million people still require urgent assistance, and renewed food insecurity in Niger, where at least 1 million people are vulnerable in coming months, as evidence of ongoing crisis.

A third of Africans are under-nourished, Oxfam said, while the number of food emergencies has nearly tripled in 20 years. Nearly half of Africans live on less than a dollar a day.

Conflicts cause more than half of food crises, Oxfam said, citing violence in north Uganda and Sudan's Darfur region.

"Darfur, where 3.4 million people are dependent on food aid, is a classic example of the devastating humanitarian emergency that conflict creates," it said.

The AIDS epidemic is taking "a terrifying toll" on one of the continent's key resources for food production -- its people. Oxfam said a fifth of the agricultural workforce in southern African countries will have died from AIDS by 2020.

And climate change is "wreaking havoc on the livelihoods of small landholders and nomadic pastoralist", the agency added, citing research that 55-65 million more Africans could be at risk of hunger by the 2080s because of temperature rises.

"The story of nearly half a century of attempts at sophisticated and sustainable solutions to hunger in Africa is not a happy one," added the Oxfam report, "Causing Hunger."

As well as supporting long-term projects, Oxfam said real solutions to Africa's food crisis should include:

- Buying aid from developing countries. "Most food aid is still imported, meaning it can take up to 5 months to deliver and cost up to 50 percent more than food purchased locally."

- Money-based schemes such as food vouchers, cash-for-work programmes or direct cash transfers.

- Increased foreign aid for agriculture, which in fact dropped 43 percent in the decade to 2002.

- More local funds for agriculture, with governments honouring a 2003 African Union pledge to increase spending on the sector to 10 percent of budgets.

"For people to be hungry in Africa in the 21st century is neither inevitable nor morally acceptable," Oxfam said.

"The world's emergency response requires an overhaul ... the stop-start approach must give way to longer-term support."