KALANDAO, Central African Republic -- The rumble of engines, any engines, is the signal for the villagers here to flee, leaving behind smoldering pots of wild roots and leaves, a meager afternoon meal.
Their haste was so great on a recent afternoon that they left something else behind - a little girl in a filthy white shirt. She wailed as she sat, utterly alone, struggling to stand, much less flee, on slender, uncertain legs.
The Central African Republic - important as a potential bulwark against the chaos and misery of its neighbors in Chad and the Darfur region of Sudan - is being dragged into the dangerous and ever-expanding conflict that has begun to engulf central Africa.
So porous are its borders and so ungoverned are parts of its territory that foreign rebels are using the Central African Republic as a staging ground to mount attacks over the border, spreading what the United Nations has already called the world's "gravest humanitarian crisis."
The situation is so bad in some places that 50,000 residents have fled the Central African Republic to find refuge in Chad, while starvation threatens hundreds of thousands who remain.
"This is the soft belly of Africa," said Jerome Chevallier, a World Bank official who is trying to help stabilize the Central African Republic. "It has little protection from whatever might strike it."
A visit to Kalandao underscores the point. The residents here had fled their country's own army, which has been burning villages to smoke out a homegrown rebel movement bent on overthrowing the government. Once the villagers realized that the approaching vehicles were from the U.N. World Food Program, they trickled back to tell their story.
"We are living in the bush like animals," Leontine Makanzi said. "Our children are dying. We are eating nothing. We have no security."
The Central African Republic, one of the poorest places on earth, has suffered through four coups in the past decade and sits almost at the bottom of the U.N. development index. In few places do people have so short a life span, bury so many of their young children or succumb to more treatable disease.
Its vulnerability has grown in recent months. On its northeastern border with Sudan, Chadian rebels supported by the Sudanese government have built a base, according to government officials and diplomats, to bolster their bid to overthrow Chad's president, Idriss Deby.
Now the Central African Republic government says these foreign fighters have teamed with local rebels to overthrow it as well, making it increasingly hard to separate one conflict in the region from another.
"The world must act now to prevent an even graver crisis here," said Jean-Charles Dei, country director for the U.N. World Food Program, which is feeding 250,000 people in the Central African Republic, one of just a handful of organizations offering any aid at all here. "The international community must act to protect these vulnerable people or risk that they will be consumed by the crisis in the region."
To stem the tide of destruction in this morass of cross-border enmity, the United Nations is examining the possibility of placing international troops to protect the borders of Chad, Sudan and the Central African Republic.
The hope is to avoid a broad, multicountry conflict like the one that swept the Congo - formerly Zaire - after the fall of Mobutu Sese Seko. That war, which followed the Rwandan genocide and pulled in fighters from countries including Uganda, Angola and Rwanda, killed 4 million people, mostly from hunger and disease. The aftermath of the conflict continues to kill 1,200 people a day.
"As long as the problem of Darfur is not solved, you will not have peace in N'djamena or Bangui," said Lamine Cisse, the top U.N. official in the Central African Republic, referring to the capitals of Chad and the Central African Republic. "The conflicts are all linked, and solving one requires solving all."
The Central African Republic is a former French colony of 4 million people sprinkled in tiny villages across a tangle of jungle about the size of Texas. Across generous swaths of fertile soil, villagers scrape together a living using hoes, water cans and human muscle. The labor required for mere survival is so strenuous that the most common operation performed by doctors at a rural hospital in the northwest is hernia repair.
On a continent where cell phone towers and fiber optic cables are finally snaking their way across the land, much of life here is lived as though the past few centuries never happened.
"It is as though the whole world has simply forgotten these people," said Sister Desiree, a Burundian nun working at a Roman Catholic mission in Ndim, a small provincial town in northwestern Central African Republic.
The four nuns at the mission, along with four nurses, some teachers and a handful of others, run a school, clinic and feeding program in Ndim, handing out food donated by the World Food Program.
Most of the people in Ndim are not displaced, but the isolation the conflict has caused, as well as the poverty of the area, has left them perpetually malnourished.
Aid organizations in Paoua, a provincial town at the epicenter of the crisis in the northwest, were instructed by the military in November to suspend activities for security reasons, so more than 50 tons of food for displaced people sat in a warehouse, undistributed.
Just outside Paoua, the remains of village after village lie in charred heaps. In one such village, behind the destroyed mud huts, deep in the forest, villagers were living beneath plastic tarps a mile from their homes.
"They came last month to give us these shelters, but they don't come again," said Pauline Koibe, who had been living in the open, sleeping under trees, since January. "It is like they have forgotten us."