Ethiopia has called on neighbouring Eritrea to withdraw its troops that it alleges are inside its territory.
The demand was contained in a letter from Ethiopia's foreign minister to his Eritrean counterpart, which also accused Eritrea of "outright aggression" saying it was conducting joint manoeuvres with Ethiopian rebels in the north and supplying them with weapons.
Eritrea has not yet commented on the accusation but has previously denied its soldiers had crossed the two countries' common border.
There has long been a history of tension between Ethiopia and Eritrea, which split off from its larger neighbour three decades ago, and there are fears of a renewed conflict.
The countries fought a border war between 1998-2000 in which more than 100,000 people died. A peace deal was never fully implemented and relations only eased after Ethiopia's Prime Minister Abiy Ahmed, who later won the Nobel Peace Prize for his efforts, travelled to the Eritrean capital, Asmara, in 2018.
