The Eritrean government says Ethiopian troops backed by tanks and artillery have crossed into Eritrea to attack Eritrean positions.

The foreign ministry described the attack as a dangerous escalation of a border dispute between the two countries.

It said this was the fourth attack by Ethiopia in less than two weeks.

A correspondent for the Reuter news agency confirmed that heavy fighting had broken out at dawn at the border town of Zalambessa.

Eritrea and Ethiopia have been massing troops and armoured vehicles along their joint border since accusing each other of invading their territories early last month.