There have been further exchanges of artillery fire between Eritrean and Ethiopian forces on the front line near the Eritrean port of Assab.

Eritrean soldiers in bunkers some seven kilometres behind the front line said the exchange lasted for about three hours on Monday morning.

Ethiopian soldiers leave for the border

They said that the Ethiopian troops had opened fire on them. But there is no independent confirmation of which side began the exchange.

Journalists were given access to a helicopter gunship which was shot down on Sunday by Eritrean troops as it came in to attack the Eritrean positions.

The Ethiopian authorities acknowledged the loss of the helicopter but said that Sunday's clashes were provoked by the Eritreans.

Port boycott

The Burre front stretches for some 40km; it is 70km west of Eritrea's Red Sea port of Assab.

Cathy Jenkins reports from Eritrea

Both sides have a heavy concentration of troops there. The solid stone wall of the Eritrean front line snakes its way across the grey, boulder strewn plain.

The port of Assab used to provide landlocked Ethiopia with an outlet to the sea, but since the border dispute started and Ethiopia began a boycott of Eritrean ports, Assab has all but shut down.

Thousands of Ethiopians who had worked in the port found themselves unemployed and crossed back over to Ethiopia.

Before the crisis blew up nine months ago, Ethiopia complained that Eritrea had moved its border posts about 4km into Ethiopian territory.

Eritrea denies this - it says it cannot understand how Ethiopia can make territorial claims on the area.