Old and widowed, Rosa Usuga lives among a despairing diaspora that has sought refuge on a muddy mountain ridge known as La Cruz. Shrouded in fog above the city of Medellin, it is a chilly slum where scores of families sleep in flimsy hovels they built from refuse after fleeing their homes in areas of Colombia wasted by war.

With little more than the clothes on her body, Usuga, 76, arrived in La Cruz last month, along with several relatives, following a massacre in her town; right-wing paramilitary gunmen had murdered 14 civilians and vowed more bloodshed. It was her third flight from the terror of civil war, the latest chapter of an odyssey that began nearly two decades ago when a paramilitary "death squad" executed her husband.

"I always feel fear, fear that another attack will happen and we will have to run again," Usuga said. "People like us are alone in this war. . . . I feel cold up here, in my soul and in my body."

The mounting ferocity of Colombia's predominantly rural war has driven hundreds of thousands of such civilians from their communities and livelihoods over the past several years, creating a vast class of wanderers left largely to fend for themselves. Although human rights advocates estimate the displaced now number more than a million -- the largest such population in the hemisphere -- they have piled up in shantytowns far from the publicity and international aid that swelled up around a similar number of ethnic Albanians driven from their homes in Kosovo last spring.

Humanitarian groups contend that the displaced people of Colombia have joined those of Sudan, Angola and Afghanistan in a netherworld of human crises left to fester because they no longer intersect -- or have never intersected -- with a political crisis that could galvanize world concern and generate help.

Colombia's displaced families have been traumatized by rebel or army incursions into their villages, by air force bombing, by death threats and land seizures by both right-wing militia groups and by the Marxist rebels the militias are fighting. The situation is further complicated because the rebels support themselves by protecting drug traffickers, who are engaged in a flourishing criminal enterprise the government is fighting with the help of 200 U.S. trainers and intelligence specialists deployed as part of a $256 million U.S. military aid program.

Some displaced families have found shelter with relatives, but most have little choice but to roam the country, usually converging on urban areas that are ill prepared to accommodate them with housing, schooling, health care or jobs. Many resort to begging, prostitution and violent crime. In the case of La Cruz, where malnutrition and illness are rampant among children, "brigades" of women regularly make the two-hour trek to and from the city below in search of food handouts.

The majority of Colombia's displaced are women and children. This is because in many instances the Marxist guerrillas and illegal paramilitary groups, which often have ties to army units, kill men they suspect of sympathizing or collaborating with the other side. The government estimates that 700,000 people who are homeless as a result of the war need some humanitarian assistance. Officials said 400,000 have been displaced over the last three years; human rights organizations say the number exceeds 1 million, 308,000 of whom were uprooted last year.

Rights workers say such people are difficult to track. Many choose not to announce themselves to local authorities when they arrive in a new area for fear they may become vulnerable to more violence or stigmatized as security risks. Consequently, they forgo the possibility of help.

"What we are seeing is similar to the consequences of a natural disaster, but it is happening every day in large numbers," said Cesar Mendoza, who is in charge of education at the Farmers' Association of Antioquia, a rights group in this province. "Misery, uncertainty and hopelessness. These are the words that have come to define these people who now have nothing."

Overall, government officials say that as many as 8 million Colombians have been forced to abandon their communities over nearly five decades of mostly political bloodshed that began with a period known as "the violence" and evolved into the present conflict, which in one form or another has been underway for more than 35 years. Most of these people are believed to have established new lives in urban locales or returned to their homes, albeit with little or no government assistance.

It was not until 1995 that the government formally made displaced people a national issue. But a report prepared in May by several U.N. offices in Colombia stated that current aid and other efforts by the government to help the displaced "have proven absolutely insufficient, causing a deplorable situation of human suffering."

Complicating matters for President Andres Pastrana's administration is the fact that this country of 38 million people is mired in its deepest economic crisis in a half-century. Furthermore, peace talks between the government and the Revolutionary Armed Forces of Colombia, the nation's largest rebel group, have faltered as violence has surged.

The uprooting of civilians, these days mostly by paramilitary groups, has accelerated as a result. In the most recent case, about 600 people fled the town of La Morelia in the province of Valle last week after militiamen killed two farmers and threatened to kill more. Observers contended the attack in La Morelia reflected a strategy used by right-wing militia groups and rebels alike to "cleanse" regions of people who they believe do not support them, then hand over the abandoned land to their followers or family members.

Because of such disruptions, farm production has dropped in several areas, and municipalities face shortages of teachers, doctors, lawyers and people willing to hold public office. In general, said Jorge Rojas, director of the Bogota-based human rights group CODHES, "The civilian population is a military target, and the impact of the situation has been very serious."

The crisis in Colombia has spilled into neighboring countries. In May, a paramilitary offensive in La Gabarra prompted about 3,700 residents to flee to nearby Venezuela. Last month, they returned to Colombia under a repatriation agreement between the two countries.

The crisis has been particularly tough on children, who often end up employed in ill-paying jobs rather than attending school. Many youngsters suffer psychological problems and illnesses because of the instability.

"The children are always sick and crying. . . . We have nothing to eat except bananas and potatoes," said Teresa Aguire, 33, a La Cruz transplant and mother of five who said her husband and sister were murdered by paramilitary gunmen. "My future is begging for my children because I cannot let them go hungry."

Fernando Medellin, general manager of the Social Solidarity Network, a government program to assist the displaced, acknowledged that in the past there were few resources and little political will to deal with them effectively. But he added that the Pastrana administration is doing more, working closely with nongovernmental organizations to distribute aid and handle emergencies related to displaced people.

The city of Medellin also is struggling to assist thousands of such people. It plans to make available 1,200 housing units and has helped several dozen families to relocate.