Islamic State (Isis) released a video on 19 April purporting to show its militants shooting and beheading what appeared to be about 30 Ethiopian Christians in Libya.
The killings were similar to past violence carried out by Islamic State, which has expanded its reach from strongholds in Iraq and Syria to chaotic Libya.
The video portrayed Christians as crusaders out to kill Muslims and then showed about 15 men beheaded on a beach and another group of the same size shot in their heads in scrubland.
Egyptian President Abdel Fattah al-Sisi ordered air strikes on Isis targets in February in Libya after the group posted a video of militants beheading 21 Egyptian Christians.
In the latest video, posted on websites supporting Isis that are seen as official, a man dressed in black clutching a pistol stood behind some of the victims.
"Muslim blood that was shed under the hands of your religion is not cheap," he says, looking at the camera. "To the nation of the cross, we are back again."
Islamic State militants have exploited chaos in the North African country where two governments allied to a host of armed groups fight for control four years after the ousting of Muammar Gaddafi.