Ethiopia's Prime Minister Abiy Ahmed has said his government is "closely following" a cross-border attack on Sudanese troops by Ethiopian forces and militia.

Sudan's army on Wednesday issued a statement saying one of its units was hit by "an ambush by Ethiopian forces and militias inside Sudanese territories", AFP reported.

There were "casualties and damage".

Ethiopia's Prime Minister has said such incidents will not break the bond between the two countries as "we always use dialogue to resolve issues".

"Those fanning discord clearly do not understand the strength of our historical ties," Mr Abiy tweeted.

The gov’t is closely following the incident with local militia on the Ethio-Sudan border. Such incidents will not break the bond b/n our two countries as we always use dialogue to resolve issues. Those fanning discord clearly do not understand the strength of our historical ties.

— Abiy Ahmed Ali 🇪🇹 (@AbiyAhmedAli) December 17, 2020

Tens of thousands of Ethiopian refugees have fled to Sudan since November when Ethiopian federal troops started fighting with Tigray regional forces.