Isis has released a video that appears to show the killing of two groups of Ethiopian Christians captured by its Libyan affiliates.
The 29-minute film released on Sunday portrays Christians as crusaders out to kill Muslims. It then goes on to show about 15 men beheaded on a beach and another 15 shot in the head in scrubland.
A masked fighter brandishing a pistol delivers a long statement, saying Christians had to convert to Islam or pay a special tax prescribed by the Qur'an.
"Muslim blood shed under the hands of your religions is not cheap," he says, looking at the camera. "To the nation of the cross, we are now back again."
The video then switches between footage of the two apparent massacres.
The film bore the logo of Isis's media arm, al-Furqan, and resembled previous footage it has released, including a video in February showing militants in Libya beheading 21 captured Egyptian Coptic Christians.
The Egyptian president, Abdel Fatah al-Sisi, ordered air strikes on Isis targets in Libya in February in retaliation for the murders.
Isis has gained a foothold in Libya as two governments backed by rival militia alliances battle each other and other extremist groups.