Ethiopia's government has declared three days of mourning after confirming that many Ethiopians held captive in Libya were killed by the Islamic State group, after the group released a video on Sunday of the killings.

The government said in a statement Monday that the days of mourning will be observed starting Tuesday and that during this time the national flag will fly at half-mast.

The statement said that Ethiopia's lawmakers will meet Tuesday to discuss the killings and consider a response.

A 29-minute video believed to be released by the Islamic militants shows at least 35 Ethiopian Christians held captive in Libya being shot or beheaded by extremists.

Redwan Hussein, an Ethiopian government spokesman, said on Sunday that he believed the victims were Ethiopian migrants trying to reach Europe.