The Adi Harush refugee camp in Tigray, which houses thousands of Eritrean refugees, was overrun by Ethiopian Federal Forces and Amhara militia.
Camp residents, speaking on satellite phones, said the guards fled after a brief exchange of fire.
All the United Nations staff had been withdrawn. The UN Refugee Agency was unable to provide an update on the situation.
In the clashes that ensued three refugees were killed and four injured. The medical condition of the injured is said to be desperate – since there is no medical aid for them.
Camp guards and some Tigrayans troops are believed to have surrendered and are being held in the vicinity of the camp.
The camp residents are very worried about their fate. Many fled from Eritrea to escape the brutal conditions under which they lived, including indefinite conscription.
They fear about what Ethiopian Prime Minister Abiy Ahmed, who is allied with Eritrean President Isaias Afwerki might do with them, if he is victorious. The automatic right to asylum for Eritreans crossing into Ethiopia was recently withdrawn.
There are reports of Eritreans in Addis Ababa being forced out of their work. Some now cower at home, fearful of arrest for being Tigrinya speakers, while those with the funds have sent their families to the Gulf for protection.