Ethiopian Christians in the video can be seen dressed in orange jumpsuits with dozens of masked terrorists standing behind them by the beach side.
The 29-minute video, which has been brought down by Youtube, shows the jihadis separate the Christians into two groups on a beach in Libya before shooting and cutting off the heads of about 16 Christians after they refused converting to Islam.
ISIS say the Christians did not pay a compulsory religious ISIS tax and were left with one option - to convert or be killed.
ISIS in the video also referred to the men as "followers of the cross from the enemy Ethiopian Church".
