The tiny braids woven into the hair of 2-year-old Ummira Idi bear the unmistakable burnt-orange hue of chronic hunger. It is a color her mother, Hassou Idi, knows all too well.

Idi, who appears to be about 30 and has ceremonial scars slashed across each cheek like cat's whiskers, has given birth to six children over the past decade. Four of them have died -- all, she believes, from malnutrition. "This one," said Idi as she cradled her limp daughter in her arms at an internationally run feeding center, "we are praying to God that she will live."

This is a nation where chronic poverty, cyclical drought and flooding, and international indifference have created conditions that are among the world's most lethal to children. One in four die before their fifth birthday.

Over the past two months, a dramatic surge of hunger across Niger -- especially intense here, in the south-central region of the country -- has further eroded the odds of survival for such children as Ummira, whose weakened immune systems are vulnerable to malaria, diarrhea and other diseases that have spiked with the arrival of seasonal rains.

Floodwaters have contaminated drinking sources and created pools for breeding mosquitoes. The pace of admissions to a regional network of hospitals and clinics run by Doctors Without Borders, an international aid group, has more than doubled. Nearly all the children brought for treatment are malnourished, with many suffering from kwashiorkor, a protein deficiency that causes telltale distended bellies and turns hair a fine, brittle orange.

Although aid groups said the food shortage here is not widespread enough to be classified as a famine, the United Nations says that 2.5 million people need donated food across this landlocked West African nation, where an estimated 200,000 children are malnourished and 32,000 are severely malnourished.

Food is also needed for 1.7 million people in nearby countries that form a band of hunger thousands of miles across the southern edge of the Sahara Desert.

Aid workers complained that officials in Niger resisted offering free food, while U.N. officials said a slow international response has deepened the crisis. They said donor governments gave almost nothing even after the drought and a locust infestation last year ensured that Niger would suffer its worst harvest in years.

In the past week, airlifts of high-energy biscuits have bolstered the stocks of the U.N. World Food Program, and truckloads of food have begun arriving in Niamey, the capital. In the past few days, feeding centers that had been open only to mothers and their children were opening their doors to all those in need.

The food shortage is a selective killer.

Just outside the feeding center run by Doctors Without Borders, where Idi and hundreds of other mothers pray for their starving children, the commercial center of Maradi bustles with people hawking bread, peanuts and rice. The aid workers and journalists thronging this city of 70,000 dine on pizza, pasta and succulent mutton in tourist guest houses.

But the availability of food does not help poor, rural children such as Ummira. They are doubly cursed by a succession of poor harvests and a sharp rise in prices that has put such staples as rice and millet beyond their reach.

In Mallamaouna Kaka, a village about 40 miles to the northeast, hungry children were playing Monday in the narrow dirt lanes among thatch huts that are home to nearly 2,000 people.

The thump-thump-thump of women pounding millet for porridge reverberated through the humid air. Luckier families sliced goat meat to grill over open fires, but many were going without food or cooking dried leaves into soup as a last resort. The next harvest is due in October.

Bassiru Haro, 27, a farm laborer, said he worried about his daughter, Sahiba, 3, who has a distended belly and orange-tinged air. Sahiba, he said, often goes for weeks without either milk or meat.

"We can't afford it," said Haro, who struggles to feed his family on the $1 a day he earns when he can find work at all. He held out his thin arms, wrinkled with sagging skin. "As you can see, I'm not well fed," he said.

Haruna Malan Garba, a senior official in Mallamaouna Kaka, said he watched helplessly as food reserves dwindled. Three years ago, he said, sacks of millet and beans filled a 10-foot-by-20-foot storage room nearly to the ceiling. By the beginning of this year, the room contained nothing but some scraps of wood and sheets of corrugated tin.

"The authorities have not done anything," Malan said. He urged international donors to give food directly to those in need rather than to the government of Niger, which he said would not efficiently deliver it. "If you give it to the government, the people may never see it," he said.

Hamassu Rabo, a farmer in his mid-forties, said his family's stocks of millet ran out three months ago after a harvest that produced one-fifth of what a good year would. As the meals grew lean and scarce, Rabo watched his youngest child, 2-year-old Baraka, develop a cough, a distended belly and a bewildered look in her eyes.

"I'm very worried," said Rabo, who has already seen four of his 10 children die in previous years. "I'm doing my best to feed my daughter. There are many families like this."

The most severely malnourished children in Mallamaouna Kaka and other nearby villages have been directed to feeding centers by Doctors Without Borders, which has screened thousands of children across the region.

Other mothers have simply arrived, with shrunken babies tied to their backs, after long bus trips or days of walking in the hot sun. Of those treated by the aid group, 5 percent have died in recent months, generally after a stay in the intensive care ward.

Ummira was not in intensive care Monday, but she did not appear to be reviving as quickly as some of the other children at the feeding center.

Her village was ravaged by drought and locusts last year. About a month ago, with food scarce, Ummira developed diarrhea. Her mother brought her to the feeding center one week ago

On Monday, a nurse handed out packets of a high-energy snack resembling peanut butter, and many children gobbled it hungrily. Lawali Mussa, a year-old boy whose rib cage was visible through the neck of his shirt, eagerly licked the brown goop from the fingers of his sister, Nana, about 6.

A few feet away, Ummira drowsed on a mat on the dirt floor. Her weary mother lay down beside her.

An infant reaches for the lips of his mother, Fatou Ousseini, at an emergency feeding center in northwestern Niger, where aid workers say that a slow international response has deepened the crisis.A malnourished boy is weighed at a makeshift health clinic in the town of Dangoma.