Sahel states are bracing for a long, potentially deadly hungry season, many weakened by the return of people from Libya who are unemployed, armed and creating fresh strife in already-vulnerable countries.

Crops have failed across a massive swathe of eight countries after late and erratic rains in 2011, and aid agencies have raised the alarm of a food crisis bigger than that which left millions hungry in 2010.

However this semi-arid belt running across Africa, separating Sahara from savannah, has had several new shocks which are aggravating the crisis.

As the rains dried up, so too did remittances from oil-rich Libya where many in this zone went to work, explains Grant Leaity, regional chief of emergency for the United Nations children's agency UNICEF.

"The money stopped, the people came back, with a significant amount of weapons," Leaity told a press briefing on Friday, adding that Niger and Malian communities had been hardest hit by the fall in remittances.

Adding to Mali's woes, Tuareg -- nomadic desert tribesman -- who returned from fighting for Moamer Kadhafi have taken up a decades-old battle for control of the north of the country.

Fighting since mid-January has sent over 20,000 refugees into neighbouring states.

"It's a clear aggravating factor. We have to find solutions, these guys are not going back to Libya," said Leaity.

Niger, which was hard hit by droughts in 2005 and 2010, saw the return of some 220,000 migrants from Libya, and is now hosting some 12,000 refugees from Mali with another 700 arriving daily, said UNICEF.

Mauritania, where up to 650,000 are facing food insecurity as a result of its worst drought in decades, has as many as 10,000 refugees.

"Communities from Mauritania and Niger are assisting the people who have arrived, but they don't have a lot to give," said Martin Dawes, UNICEF's regional communication adviser.

Also facing crises are Chad, Burkina Faso, Senegal and northern parts of Cameroon and Nigeria where the situation is complicated by terrorist activities by Islamic sect Boko Haram.

UNICEF has estimated more than one million children under five will need treatment for severe acute malnutrition which leaves them visibly wasted and in need of weeks of supervised treatment at a minimum of $80 per child.

The organisation has asked for $67 million (50 million euros) from donors for the first half of the year, as the so-called "lean season" is expected to arrive in March and last until August. It has received $10.3 million so far.

In January the EU announced it was doubling aid to the Sahel to 95 million euros in a "race against time" as 23 million people began 2012 facing "huge uncertainty about how they will feed themselves and their families."

With food production deficits as high as 52 percent compared to last year, the EU warned early action is needed to "reduce the risk of it turning into a major disaster."

These nations, most on the bottom of the UN Human Development Index and in one of the poorest, most environmentally damaged parts of the earth, were hard-hit by soaring food prices in 2008, which have not dropped.

Most people survive off agriculture and livestock, and desertification as a result of climate change, diminishing water resources and population growth have put more people in conflict for scarcer resources.

In Mali, where huge lakes have dried up, some towns are "emptying out" as it becomes unsustainable to survive there, said Leaity.

This is the third drought in the Sahel in a decade, and while previous ones were felt mostly in Niger and parts of Chad, the food crisis this year is unfolding across the entire region, said the WFP.

While UNICEF wants to treat severe malnutrition in children in the short term it has highlighted the need for a more sustained response "to interrupt a terrible cycle" which is killing children.

"A major tragedy in the Sahel can be averted if there are the resources and children get the treatment they need from trained staff," according to the agency.