Each side was reporting more than 10,000 enemy dead, wounded or captured since the fighting flared one week earlier on parts of the front, which is some 1,000 kilometres (600 miles) long.

Their claims were impossible to confirm, but a western diplomat in the Ethiopian capital told AFP Tuesday: "there is now significant and intense ground fighting." He said the fighting was likely to continue until one or other side obtained a strategic advantage.

Another diplomat suggested the two countries might have changed options and given up on diplomacy.

The Eritreans claimed in a statement that more than 18,000 Ethiopian troops were "put out of action" between Monday and Thursday. "Ethiopia has also lost two MiG-23 jet fighters, one Mi-35 helicopter gunship and five tanks" in the fighting on the western front, it said.

On Sunday, Ethiopia claimed that more than 8,200 Eritrean troops had been killed, wounded or taken prisoner between Wednesday and Saturday, and on Tuesday officials in Addis Ababa said the Eritreans had suffered "heavy human and material losses".

Each side claimed to have repulsed attacks by the other. The last clashes, on May 25 and 26 around the Mereb river on the western front, caused hundreds of fatalities and thousands of wounded, according to both Asmara and Addis Ababa.

The conflict between the neighbouring states ignited in May 1998 around a border dispute that followed protracted tension over several economic issues between Ethiopia and Eritrea, its former Red Sea province which had gained full independence five years earlier.

Andemichael Kassai, the number two in Eritrea's foreign ministry, told the Eritrean News Agency on Tuesday that the Ethiopians "intend to wage war for reasons far beyond the border conflict," implying that Addis Ababa wants to topple the government of President Issaias Afeworki.

The war has been characterised by large-scale battles where both sides claim to have inflicted thousands of casualties on the enemy. Numerous skirmishes have also been reported.

The two countries have mobilised troops and stocked up on weapons and ammunition since the last big battle, in February, when Ethiopian troops recaptured the western front hamlet of Badme, occupied by the Eritreans at the beginning of the war.

Observers say both countries appear determined to win a strategic advantage before the three-month-long rainy season, due to start any day now.

"Eritrea is determined at all costs to reconquer Badme," an Ethiopian official told AFP.

Both sides have accepted an Organisation of African Unity (OAU) peace plan which provides for demilitarization of the border, deployment of peacekeepers, and neutral demarcation of the frontier.

But that plan has long been moribund because the rivals are dug in behind their own interpretations of it, and Ethiopian leaders have made it clear in numerous statements that they intend to fight on unless the Eritreans withdraw from all disputed territory.

The OAU plan calls specifically for Eritrea to withdraw from Badme and its environs, but Ethiopia's leaders told the OAU that they interpreted this to mean that Eritrea must withdraw from the other disputed locations as well, which they refuse to do.

The presidents of Libya and Egypt and special envoys from the United States and the United Nations have all tried to bring peace between the two countries on the basis of the OAU plan, but have run into brick walls in both capitals, and little diplomatic action has been reported over the past month.

The foreign ministry said Ethiopia had also lost two MiG-23 jet fighters, one Mi-35 helicopter and five tanks since fighting in their year-old border war resumed on the western Mereb-Setit front last Thursday.

Ethiopian government spokeswoman Selome Taddesse told Reuters the claims were ``highly exaggerated'' and that ``Eritreans are being beaten back badly, suffering heavy casualties.''

There was no independent confirmation of either claim as journalists and other observers have been barred from the border area on safety grounds.

But Eritrean television has shown footage of what appeared to be an Ethiopian helicopter gunship being hit in mid-air and crashing in flames to the delight of Eritrean soldiers.

New footage aired on Monday night showed Eritrean heavy artillery and mobile rocket launchers pounding Ethiopian positions in the hills and Ethiopian artillery units returning heavy fire. The crackle of Eritrean machine gun fire could be heard above the whistle of incoming artillery.

Eritrean presidential adviser Yermane Gebremeskel said both sides continued to pound each other's positions on Tuesday. ``The fighting is still very intense,'' he told Reuters.

Eritrea's foreign ministry said 2,060 Ethiopian soldiers were killed and 4,050 wounded in battles on Sunday and Monday, ``bringing the total number of Ethiopian troops put out of action in five days of intense fighting to over 18,000.''

On Monday, Selome said a total of 8,200 Eritreans had been killed, wounded or captured, and denied the loss of the MiGs.

The border war began in May 1998, when Eritrean forces took control of two sections of disputed border land, including the Badme region, in six weeks of fighting.

It flared again in February this year and Ethiopian forces then retook Badme.

Tens of thousands of soldiers are believed to have died in the war between the two former allies and diplomatic sources put the total number of troops deployed in the current battle at around 70,000.

Since the conflict began, Eritrea has mobilised over 250,000 troops, both men and women, from a population of 3.5 million and most Eritreans have at least one relative on the front line.

Diplomatic and military sources in Asmara say the current fighting on the Mereb-Setit front is for control of strategic high ground which secures access to the Badme region.

``The crucial point is to be in the good positions when the rainy season comes,'' a Western military analyst told Reuters.

``Following successive marginal harvests in recent years in the northern region, and a complete failure of this year's short rains, more than 13,000 persons...have migrated in south Tigray and northern Wollo alone,'' the U.N. Development Programme (UNDP) said in a statement issued in the Ethiopian capital.

The agency warned that a ``grave famine situation'' was developing in the eastern region of Hararghe.

The year-long border conflict between Ethiopia and Eritrea has also undermined agricultural production, with tens of thousands of rural families displaced from their farms, UNDP said.

In towns across the north and east, destitute women and children have had to resort to begging.

Ethiopia has appealed for 360,000 tonnes of food aid for an estimated 4.6 million people facing food shortages because of drought.