NAGFA, Ethiopia— ''The tanks ran over the people and ground them up,'' Amena Mohammed remembered later. ''Bodies fell over us. I covered the two children with bloody clothes and pretended to be dead. We hid among the dead bodies for three days.''
The 28-year-old woman is one of hundreds of thousands of Eritreans turned into refugees by Ethiopian attacks on civilians over the last four months, a refugee tide that, along with an Ethiopian ban on foreign relief workers, increases the danger of food shortages and starvation.
Responding to a string of victories in which the rebels broke out of nine years of stalemated trench warfare and overran the main army headquarters at Af Abed, the Ethiopian regime this spring began a campaign of bombing and raiding civilian villages so as to use hunger as a weapon by creating refugees, according to the guerrillas.
''Practically the entire population has been driven out of this area,'' said Gebremichael Mengistu, the field coordinator for the rebels' Eritrean Relief Agency, unrolling a map and pointing out a sector beginning near the port of Massawa and running north and inland to Af Abed. ''We estimate 350,000 to 500,000 have now fled, the overwhelming majority in the Asmara-Massawa-Keren triangle, a relatively densely populated area.''
Amena Mohammed, the woman here in Nagfa, sat in a small tent, holding her infant daughter, Halema, on her lap, recounting what happened when the Government soldiers entered the village of Sheeb on May 12.
''When the Amhara came,'' she said, using the name of the dominant ethnic group of Ethiopia, ''they surrounded the village with tanks, about 15 of them, and called for the people not to run, to come to a meeting. But then the tanks drove over the people, and the ones that ran away they shot with machine guns.
''They just killed,'' said the young woman, who lost a 4-year-old son, her mother and two sisters. ''They killed the animals and burned the houses and then they went to loot.''
The Eritrean People's Liberation Front says about 400 people were killed in Sheeb, about 80 of them run over by tanks. It was one of the most grisly incidents in the 27-year-old war waged by Eritreans trying to break away from the Soviet-backed Ethiopian regime of Col. Mengistu Haile Mariam. [ Amnesty International has accused the Ethiopian Army of killing more than 1,000 civilians in recent weeks in Eritrea and Tigre provinces. ''The Ethiopian armed forces have committed absolute massacres, killing hundreds of defenseless civilians,'' an Amnesty International report issued in Rome said. ] Food Supply Affected The refugee problem is particularly devastating because of its effect on the food supply, said Mr. Gebremichael, the relief official. ''The important thing is that this is the surplus-producing area, this is what people depended on to provide the margin of food,'' he said. ''Now they will produce nothing.'' ''In addition the Government has declared 10 kilometers all along the coast a free-fire zone where nobody can go,'' he said. ''This is land nomads use for grazing, and there are also places in the highlands used in the winter by farmers from other areas.''
''This is a deliberate policy of starving the people by the Ethiopian Government,'' the relief coordinator said. ''The famine generally has been man-made, not an act of God but an act of politics.''
Famine is a constant specter in this part of the world, where the effects of frequent droughts are compounded by nearly constant internal warfare. Because of the battles, Somalians and Christian southern Sudanese have fled into parts of Ethiopia, while about 700,000 Eritreans are in the Sudan. Ethiopia backs the Sudanese rebels, while the Sudan aids the Eritreans.
''You don't see widespread malnutrition, although there is some,'' said Mr. Gebremichael, the relief coordinator. ''We don't have reports of death from starvation.'' Potential for Disaster
But there is potential for disaster. Mr. Gebremichael said last year was a bad year, resulting in a crop deficit of the equivalent of about 450,000 tons of wheat and other produce. This year was dry too, although there have been recent heavy rains.
The situation had not appeared as bad as the 1984-85 famine, he said, for several reasons. That drought had been preceeded by several bad seasons so people were already weakened. And there are now systems for supplying outside aid, including an efficient relief network run by the Eritreans themselves, that did not exist then.
The flight from the food-producing areas, however, has drastically changed things.
''It means that 1989 will be a famine year,'' Mr. Gebremichael said.
The food supply is also threatened by a plague of locusts moving through northern Africa, and by army worms, a kind of caterpillar.
Consulting his figures at the Eritrean Relief Agency's headquarters in a lowland area called Himbol, he said the Government policies would eventually affect about 1.7 million people, including nomadic herdsmen, a figure close to the 2 million the State Department says are endangered. Four Refugee Camps Set Up
Since May, the Eritrean relief group has provided for 56,000 new refugees in four camps it has set up, with others waiting not far from their home villages.
''We can feed these people until the end of August, perhaps the end of September,'' he said. ''They need blankets, household utensils, tents or shelter, medicine, everything.''
Mr. Gebremichael said the Ethiopian Government's ordering out of foreign aid workers virtually dismantled the aid system set up after the earlier famine received worldwide attention.
This spring the United States broke with its previous policy of not sending aid directly to Eritrea and arranged for cross-border shipments of aid through a private agency, Lutheran World Relief. Mr. Gebremichael said about 40,000 tons of food was expected.
Most of the support for the Eritrean relief program, he said, comes from the organizations of Eritreans living and working abroad and from private charity organizations in Norway, West Germany, Australia and Canada, among other countries.
''Our support comes totally from Western countries,'' Mr. Gebremichael said. MIG's Bomb Rebel-Held Town
After the Eritrean guerrillas took Af Abed, which had been the headquarters of the Nadu or ''Destroyer'' Corps in March, the Ethiopians sent their MIG's to bomb the market town.
Three people were killed and a half-dozen buildings flattened. The town and the environs were emptied, as people abandoned their fields and shops to hide in the surrounding hills.
This, the Eritreans say, is the pattern: On March 31, MIG's bombed the village of Melebso, killing 15 people and wounding 25 and burning five houses; on April 2, they bombed Mensae Bet Shehaqu, killing 5 people and burning 8 houses; on May 3, they used napalm on Halhal, burning 10 houses; on May 6, 5 other villages were bombed, and so on.
In a recent two-month period, about 350 civilians have been treated for serious wounds, from bullets, napalm, land mines and cluster bombs, at the central hospital of the Eritrean People's Liberation Front, according to Dr. Assefaw Tekeste, the director of civilian health services.
The names of the abandoned villages appear in the notebook kept by Osman Adem, the Eritrean relief director in a mountain ravine near here where about 8,780 people have gathered in the last few months. Some Arrive on Camels
Refugees are still coming in, some on camels with suitcases and transistor radios strapped to the hump.
''Even now the planes are not searching for the fighters; they are searching for the civilians,'' said Mohammed Sayyed, a 65-year-old farmer who fled from Af Abed leaving all his possessions behind after the bombing.
''We are not deaf,'' he said. ''We can follow what they do on the Ethiopian Government radio. They say that to catch the fish they must dry up the pond.''