ASMARA, Eritrea, June 6 (Reuters) - Eritrea and Ethiopia braced for more air raids on Saturday after hopes of an internationally-brokered peace between them were shattered by omens of all-out war.
The neighbours in the horn of Africa launched warplanes on tit-for-tat bombing raids against each other on Friday, with Eritrea inflicting more casualties in an attack on a northern Ethiopian town but Ethiopia striking right at the heart of the Eritrean capital.
Other African nations pleaded with two of the continent's poorest countries to halt their escalating conflict, while the United States protested that attacks on the airport in the Eritrean capital endangered foreign nationals trying to flee.
Eritrea late on Friday refused Britain permission to send a second charter flight to the capital to evacuate 60 Britons stranded there. An earlier flight was taking 59 Britons and around 100 Americans from Asmara to Germany via Egypt.
Eritrean warplanes bombed the northern Ethiopian town of Mekele at least twice on Friday, officials said, killing at least 40 people and wounding more than 100.
Ethiopian officials said an airport under construction in the nearby city of Axum had also been bombed, but there was no independent confirmation.
Ethiopian jets in turn struck twice at Eritrea's capital Asmara, hitting both the military and nearby civilian airports.
It was not clear who launched the first attack, with both sides accusing the other of indiscriminately bombing civilian targets.
An Ethiopian MiG 23 was downed by Eritrean gunfire during the Asmara raid, sparking wild celebrations in the capital. One person was killed and four injured by shrapnel as they waited in a bus queue outside the airport and a Zambian Airlines cargo aircraft parked on the runway was also hit.
Earlier in the day the Eritrean government had appeared to cautiously accept an international four-point plan to settle its bloody border row with Ethiopia, but said ``serious issues of detail'' still needed to be worked out.
Ethiopia had on Thursday accepted the plan -- brokered by diplomats from the U.S. and Rwanda -- which calls for troops from both sides to withdraw from disputed territory, for an observer force to be deployed, for the return of civilian administration to disputed areas and for an investigation into the roots of the conflict.
U.S. State Department spokesman James Rubin condemned Friday's air raids and said they had sharply escalated the conflict.
``We call on both Ethiopia and Eritrea to cease all hostilities while facilitators seek a peaceful resolution to the dispute,'' he said in a statement.
Ethiopia and Eritrea have argued peacefully over their border for years, but the dispute turned violent on May 6 with each accusing the other of invading.
The row centres on a rocky 400 square km (155 sq mile) triangle of land which both countries claim, although Eritrean forces have also crossed into territory which is indisputably Ethiopian.
Both sides have mobilised veterans of the guerrilla struggle which overthrew the Ethiopian military dictator Mengistu Haile Mariam in 1991.
Eritrea was rewarded for its efforts with independence from Ethiopia following a referendum in 1993 and the two countries were on friendly terms until the border disagreement turned violent.
Ethiopia has told Eritrea to cut the size of its embassy in its capital Addis Ababa to three and has given all other diplomats until Sunday to leave.
Libyan leader Muammar Gaddafi has proposed deploying troops from Libya and other Saharan African states in the disputed border areas, Libyan state-run television reported.