By Martin Plaut BBC, London

Ethiopia is unhappy about the border ruling

The soldiers entered the temporary security zone on the Eritrean side of the border on three occasions to play football.

They refused to leave before the end of their games, despite repeated requests from UN troops monitoring the ceasefire that ended the Eritrean-Ethiopian border war.

The temporary security zone runs for 1,000 kilometres along the Ethiopia - Eritrea border and is overseen by some 4,000 UN troops.

Tension

Both countries have highly disciplined armies, which have been careful not to infringe the zone in the past.

But tension on the border is increasing.

Ethiopia is deeply unhappy that the village of Badme that sparked off the border war has been awarded to Eritrea.

Ethiopian Prime Minister Meles Zenawi is under pressure from his political critics as demarcation of the border, due on 1 October, draws closer.

Unofficially Ethiopian officers have apologised about the incursions - but the UN is taking the incidents very seriously indeed.