For two years the war has been fought in short, fierce bursts along a thinly populated border. But today aid agencies reported that 250,000 civilians had been displaced by fighting around Barentu, the regional capital, which Ethiopia captured today after a three-day bombardment.

This evening, the Eritrean government made a much higher estimate of refugees: 550,000.

Either number is huge for Eritrea, a poor nation of 3.5 million people. With about 800,000 people already short of food, Eritrea may face a new scale of problems, after already having lost 10,000 or more of its soldiers.

Tonight, Ethiopian state television reported that Ethiopia had bombed military targets near Massawa, Eritrea's main port, at the Red Sea, at least 80 miles from the dusty, narrow strip of border in dispute.

The Ethiopian president, Meles Zenawi, said today that his troops would continue to chase Eritrean soldiers anywhere in Eritrea until they retreat from land along the border that Ethiopia claims.

"To achieve this, we do not share the point of view of some military experts who suggest that the shortest distance between two points is a straight line," Mr. Zenawi told the BBC in an interview in the capital, Addis Ababa. "On the contrary, it may be that the indirect route is the shortest route."

Although he said that Ethiopia had no designs on Eritrean land, Eritrean officials cast the fighting as an outright invasion.

"We will reverse it," said Yemane Ghebremeskel, an aide to Eritrea's president. "It may take some time, but I am sure we will prevail because no Eritrean will accept an Ethiopian invasion."

Last Friday, Ethiopia launched an offensive against Eritrea, once a close ally and, until it became independent in 1993, the northernmost province of Ethiopia. In the days before, Mr. Zenawi warned diplomats that he wanted a quick end to the war, which has cost at least 20,000 lives on each side and vast amounts of money. The Ethiopian president conceded that the war was hampering efforts to feed eight million Ethiopians who face severe shortages of food from a drought.

The war began in May 1998 with disputes over a triangle of land known as Badme. Eritrea, claiming the land under colonial treaties, moved in troops. Ethiopia called that an invasion. Since then, Ethiopia has regained much of the land, but Eritrea has accused Ethiopia of dragging its feet on a peace accord brokered by the Organization for African Unity.

This morning, after two days of heavy artillery exchanges, Ethiopia seized Barentu, 43 miles north of the Ethiopian border, cutting off the second of two main supply routes for the Eritrean Army to the western front. With Barentu's capture, Ethiopians say, the fighting is effectively over in western Eritrea, and now the Ethiopian Army is likely to move toward a central front, which is heavily fortified.

Both armies are well equipped and trained, so the fighting has been intense, with aerial bombings and artillery and tank battles as well as hand-to-hand fighting. Here in Shelalo, which was one of the first towns the Ethiopians attacked on Friday, an Eritrean prisoner, Amine Abe, 22, said he had been caught in heavy fighting near Barentu, where he had been sent with huge reinforcements.

He was shot three times: in the left leg, left side and shoulder. He said he did not expect such force from the Ethiopians.

"I was a bit shocked," he said, lying bandaged on a plastic tarp in a hut with four other wounded Eritreans. "They were strong."

Mr. Ghebremeskel, the Eritrean president's aide, said the Ethiopians had advanced by fighting in huge numbers along areas with far fewer Eritreans.

"At the end of the day," he said, "it's a mere issue of numbers."

Since the fighting entered this region, civilians have started fleeing along with the retreating Eritrean Army. But today after the Eritreans left Barentu the numbers exploded.

Lindsey Davies, a spokeswoman for the United Nations Food Program, estimated the number of people fleeing at 250,000. She said they were scattered around the countryside. She said her agency was without supplies to give the refugees more portable food than is given to people in refugee camps.

"So we are going to have to look elsewhere in order to get that food into Asmara," she said. "But then we will have another set of challenges because we'll have to see how we can move that food into the interior."

The war has worsened food shortages, particularly in Ethiopia, which faces a far more serious drought problem. More than 200,000 people have already been pushed from their homes around the border in the last two years.

Today, Yirgalem Abraha, a 20-year-old woman who has lived for two years in one of the camps for the displaced, said she did not receive food this month and so has begun to sell coffee and tea in front of her hut. Because of the new fighting, the United Nations has suspended food deliveries in the area. She is not sure how she will feed herself if the fighting goes on.

"I don't make much," she said, at her camp, near the town of Wala Nehbee, on the border with Eritrea. "It's just me surviving."