ASMARA (Reuters) - Eritrea said on Monday its forces shot down two Ethiopian MiG-23 jet fighters in the latest battle of a year-old border war between the two Horn of Africa states. Eritrean presidential adviser Yermane Gebremeskel said the two MiGs were downed on Sunday and that Ethiopian losses had mounted steeply in five days of fighting on a central section of the main Mereb-Setit military front. He said over 12,000 Ethiopian troops had been killed, wounded or captured in the new round of fighting and that Ethiopia also lost one MI-25 helicopter gunship and five tanks. Eritrean television showed new 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. Ethiopia claimed on Sunday to have killed, wounded or captured over 8,000 Eritreans on the front but there was no way to verify either claim. Tens of thousands of soldiers have been reported killed in a war that began in May 1998, when Eritrean forces took control of two sections of disputed border land in six weeks of fighting. It flared again in February, when Ethiopian forces retook part of a front at Badme on the Mereb-Setit river. The Organisation of African Unity (OAU) has led efforts to end the war between the two former allies. Both sides accept an OAU peace plan but disagree over its details and implementation. Yermane said the war‘s two other fronts remained quiet on Sunday aside from some shelling on the Zalambessa front. Zalambessa, occupied by Eritrea last year, is a border town south of Asmara which both sides claim. Military analysts in Eritrea say they expect a major confrontation in the area since Ethiopia has stated it would retake Zalambessa if Eritrea refused to withdraw. Eritrea gained independence from Ethiopia in May, 1993, after a 30-year independence struggle. President Isayas Afewerki of Eritrea and Prime Minister Meles Zenawi of Ethiopia were considered close allies until the outbreak of the war.