Ethiopia and Eritrea must exercise restraint and defuse tensions, the UN warned on Wednesday after fighting erupted on the disputed border between the two nations.

UN Secretary General, Ban Ki-moon met with Ethiopian Prime Minister, Hailemariam Desalegn in Brussels.

The UN Deputy Secretary General, Jan Eliasson, called the Eritrean foreign minister to express concern and call for a peaceful resolution.

"They urged both governments to exercise maximum restraint and refrain from any act or statement that could exacerbate the situation", said Stephane Dujarric, Ban's spokesman.

Clashes broke out on Sunday and Monday between the two countries.

Ethiopia said it had repelled an Eritrean attack, while Eritrea said its army had taken proportional measures against an attack on the border on Sunday.