A video purportedly made by Islamic State and posted on social media sites on Sunday appeared to show militants shooting and beheading about 30 Ethiopian Christians in Libya.

Reuters was unable to verify the authenticity of the video, but the killings resemble past violence carried out by Islamic State, an ultra-hardline group that has expanded its reach from strongholds in Iraq and Syria to conflict-ridden Libya.

The video, in which militants call Christians "crusaders" who are out to kill Muslims, showed about 15 men being beheaded on a beach and another group of the same size, in an area of shrubland, being shot in the head.

Both groups of men are referred to in a subtitle as "worshippers of the cross belonging to the hostile Ethiopian church".

Libyan officials were not immediately available for comment.