The 15,000 Salvadoran refugees in this and nearby villages are supposed to be safe. This is Honduran territory. The carnage that takes place daily across the border a few miles away is supposed to end at the surveyor's line. But it doesn't.

On March 18 a terrified mass of refugees, estimated to number 4,500, under fire from Salvadoran helicopters and mortars crossed the Lempa River into Honduras.

While several attacks on refugees have been charged, witnesses have proven difficult to find. But in this case, in addition to the thousands of survivors, international refugee officials were on the scene during two helicopter sorties. One of the officials recalled:

"Right at the end, a boy was running along the bank and the helicopter came in front of him and looked at him. And that was where the bomb [apparently a hand grenade] was thrown and that bomb killed a woman. I saw her covered with blood. She was only about two meters away from me. And it also hit a little girl."

The helicopter left, said the official, who asked not to be named, "and I got up and saw that there were now other bodies around." While the number of casualities among the 4,500 crossing the river that day was limited, about 30, there was more to come on the Honduran side.

Within the next five days, at least 19 of those refugees were killed and several more "disappeared" at the hands of the Honduran soldiers on this side of the border, according to relief workers in the area.

While overall, the casualties do not approach what a Salvadoran colonel once called "industrial quantities," the crossing and its aftermath suggest how perilous the situation has become for refugees along this border. El Savador contends that those pursued by its troops are not refugees but guerrillas and if they are unarmed, it is because they have abandoned their weapons to seek refuge so as to fight another day.

Those crossing the Lempa River clearly were not armed, and the majority, by all accounts, were women and children.

Until recently refugees tended to flee El Salvador in relatively small groups. Now as the Salvadoran government wages a slow but massive counteroffensive against the guerrillas with increasingly plentiful U.S. arms and training, the refugees are fleeing former guerrilla strongholds and "liberated zones" en masse and many head for Honduras.

The guerrillas have traditionally been strongest in the rough, mountainous terrain near the Honduran border, where most of the refugees now around La Virtud come from.

In these isolated areas where roads are rare and life lived at the edge of survival, the peasants of El Salvador are often closer, even to the extent of family ties, to the Hondurans across the border than they are to the rest of their countrymen.

The 1969 Honduran-Salvadoran war was fought in part because tens of thousands of Salvadorans had moved from their own overcrowded country into less densely populated Honduras. The migration was considered a "safety valve" by El Salvador and an intolerable burden by Honduras. It ended with the 1969 war.

Now many Hondurans fear that the refugees may be starting the migration again. And indeed many have moved in with stick and thatch ranchos or rented Honduran land, openly preparing for a long stay.

"We started hearing bombs and mortars on Sunday, March 15," said Tito Sanchez, 30, one of those who was soon to cross the river. "We put rocks up around the doors and stayed on the floor for two days."

At the time, the Salvadoran Army was reporting confrontations with guerrillas near the town of Villa Victoria, not far from Sanchez's settlement of Santa Marta. Sanchez and others said they saw no evidence of guerrilla acitvity.

On March 17, peasants all over the area were abandoning their homes and heading for Honduras. Thousands gathered on the arid slopes near the banks of the Lempa at a crossing known as Piedras Coloradas. Few could swim and few were tall enough to wade across the wide, clear stream. Using ropes and a few inner tubes they began the crossing one by one, two by two.

By the following afternoon, some of the French doctors and other relief officials had arrived on the scene. An emergency hospital was set up, while some of the officials waded into the waters to help.

"There was a lot of confusion and then I heard the noise of the helicopter coming," said the official interviewed. "People hid themselves where they could among rocks, between boulders, under tress, of which there are precious few there. And the helicopter arrived and began to drop bombs."

From this and other witnesses' descriptions of the explosions it appears the bombs were most likely grenades thrown or shot from launchers inside the helicopter.

"The noise was infernal," said the official. "The river is boxed in there among the mountains, and there was a lot of echo. Bombs and machine-gun fire on both sides of the river, the Salvadoran and the Honduran.

"How long it lasted I don't know. To me it seemed an infinity of time . . . when they got tired of shooting they left.

"The great contingent of people had crossed already, and 300 or 400 were working their way up a little ravine to where the emergency hospital was. They went under the trees because from the Salvadoran side a mortar was shooting constantly at intervals of 10 to 15 minutes. So when you heard the sound of the shell coming people threw themselves down and hid. When the shell exploded they started walking again.

"Then after a while the helicopter came anew. I don't know if it was another or the same, but it came back and started shooting again, the same kind of operation."

This particular official left the river at 5 p.m. But others continued helping the refugees come across until the last of them made it beneath a bright moon at 10 o'clock.

The official began organizing the refugees gathered at the emergency hospital for the hike to Los Hernandez, the nearest Honduran village.

"The Honduran soldiers had already marched onto the scene," said the official. "They were watching from the mountain whose slope leads down to the river.

"About one kilometer from [Los Hernandez] we came across a body," the official said. About 500 meters on were the clothes from another body and a bit beyond that the pool of blood from someone else who had been killed. There in the afternoon they killed three," the official said.

"That night Honduran soldiers surrounded the town. As we left the village to go to La Virtud, at the exit of the town they had about 15 or 20 people tied up and stripped. Those have disappeared.

"On the following morning eight bodies were found in a little ravine to the west of Los Hernandez and another nine between Los Hernandez and La Hacienda, seven of them dead from bullets and two from apparent torture."

The Honduran government says it does not kill refugees. But many people here make a detailed case that suggests at least some of its soldiers do. Army officers now on the scene would not talk to reporters.

Contacts and cooperation between the Honduran and Salvadoran armed forces have grown steadily over the last two years, partly encouraged by the United States and Organization of American States representatives seeking to cool frictions dating back to a brief 1969 war, and partly because both armies are adamantly opposed to the kind of leftist guerrilla movement now fighting to overthrow the Salvadoran government. The two countries finally signed a peace treaty after lengthy OAS mediation last year.

The only protection these refugees now have comes from the moral authority of relief officials working here in connection with the Office of the U.N. High Commissioner for Refugees.

Privately these officials say it is an ongoing battle.

"Constant vigilance is required on a protection level," one concerned U.N. bureaucrat in the area noted recently.

"A child dies here every day," said a doctor looking at a frail, days-old patient stretched limply on a folding cot in one of the prefabricated wooden huts that serve as the hospital here. The baby's eyes were listless, unmoving. Tiny plastic tubes ran into its nose and arm.

"This one is dying too," said the doctor. "Some days we lose two children, but every day we lose at least one. More than 40 have died since they crossed the Lempa. They die from diarrhea and dehydration and exposure. They die from sheer weariness."

"The real atrocity is the fear -- the terror -- that is in this camp," said Vincent Jeannerod, 31, the regional coordinator for Doctors Without Borders, a group of French doctors and nurses working with the U.N. group here.

"These people lost everything," said Jeannerod. "They are coming to us with nothing except, more than anything, fear. Even inside our camps they are afraid.

"You can say you are giving anything to these people, but they don't believed you. Sometimes they say the only kind of help they know is guns and death. 'Because the Army comes,' they say, 'and the Army talks of agrarian reform and the peasants who believe them, the Army orders them killed. The guerrillas who come talk of liberation and then the airplanes come and bomb and kill and the gurerrillas can't do anything.' They say that a lot," said Jeannerod.

The problems of Salvadoran refugees rapidly becoming a problem for the entire region. U.N. sources estimate the number of Salvadorans who have fled their country because of the war as anywhere from 180,000 to 300,000. Six months ago there were only 33,000. Now there are that many in Honduras alone.

Every country in Central America, as well as Panama, Belize and Mexico, now has substantial numbers of Salvadoran refugees. Uncounted numbers more go to the United States as illegal aliens. At present only about 25 percent of the refugees are receiving any substantial international aid.

The estimated 100,000 displaced persons still inside El Salvador are entirely dependent on the Salvadoran government and various church organizations for help. The U.N. agency is not involved.