Ethiopia says its forces have attacked a military base inside arch-rival Eritrea, in what Ethiopia calls an act of retaliation.

Government spokesman Shimeles Kemal says Ethiopian ground forces moved 16 kilometers into Eritrea late Wednesday and launched what he called a “successful attack” against a military post used by “subversive groups.”

Shimeles, speaking at a news conference in Addis Ababa Thursday, said the attack did “not constitute a direct military confrontation between armies,” but gave no further details on the operation.

There has been no word on casualties or damage from the attack, and no immediate comment from Eritrea.

Ethiopia has repeatedly accused Eritrea of sponsoring rebel groups that attack targets in Ethiopia's Afar area. Shimeles specifically mentioned an incident in January in which five European tourists were killed.

Ethiopia and Eritrea fought a war between 1998 and 2000 that killed an estimated 80,000 people. Tension between the countries has remained high ever since.