UN peacekeepers are stationed on the border

The Eritreans say they are for agricultural and construction purposes.

Tensions between the two countries are running high after Ethiopia rejected a recent ruling that the disputed town of Badme belongs to Eritrea.

Some 80,000 people died during the bitter two-year border war between Ethiopia and Eritrea but the UN mission is seeking to downplay the development.

Ten per cent of Eritrea's population are thought to be in the army and they are often deployed in non-military activities, says the BBC's Jonah Fisher in Eritrea.

However, he says the movement of soldiers west is significant because it is where the town that triggered the last border conflict - Badme is.

Ethiopia is currently in control of Badme but rejected a decision by an independent boundary commission that the small town belongs to Eritrea.

Tense

UN representative Gail Bindley-Taylor Sainte said there were formations going across from the central sector and other parts of Eritrea.

Peacekeepers feel the heat

"We have numbers but we cannot disclose numbers to you, that is military intelligence," she said.

"The situation appears to be tense, more tense than it has been before," Ms Bindley-Taylor Sainte added.