The Ethiopian military has been fighting rebellious local forces in the northern region of Tigray, which borders Eritrea and Sudan.
Abiy's government set a 72-hour ultimatum on Sunday for the TPLF to lay down its arms or face an assault on Mekelle, the highland regional capital city of 500,000 people.
If the Tigray People’s Liberation Front refuses to concede in the three-week-long war, there could be a bloodbath, foreign governments and humanitarian groups say.
The Tigrayan forces' leaders could not immediately be reached for comment but have previously denied any responsibility for the massacre.
Here are details on who has influence in Ethiopia and whether they are using it.
Foreign Minister Gabi Ashkenazi worked with his counterpart in the region to secure the release.
Accusing neighboring Eritrea of sending tanks and thousands of troops into Tigray in support of an Ethiopian government offensive, Gebremichael said his forces were under attack "on several fronts."