Ethiopia attacks camps inside Eritrea
From 1998 to 2000 Eritrea and Ethiopia fought a border war in which about 80,000 people died. The Ethiopian government claims that Eritrea harboured subversive groups that were being trained for missions in Ethiopia.
Eritrea has also been accused of supporting Islamist Al-Shabab in Somalia as well. Ethiopia earlier entered into Somalia to try and help stem the rebellion. The Ethiopians were no doubt encouraged in their adventures by the U.S.
So far the Eritrean government has not commented on the attack that was directed at several camps in Eritrea. This is the first attack in Eritrean territory since the end of the border war. The Ethiopians see Eritrea as helping rebels in the Afar region. For more see this article.