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.
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.
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 attack widens the circle of nations affected by the group's atrocities while showing its growth beyond a self-declared caliphate in Syria and Iraq.
The release of the 29-minute video comes a day after Afghanistan's president blamed the extremists for a suicide attack in his country that killed at least 35 people and underscores the chaos gripping Libya after its 2011 civil war and the killing of dictator Muammar Gaddafi.
Both groups of men are referred to in a subtitle as "worshippers of the cross belonging to the hostile Ethiopian church", Reuters reported.
Ethiopia said it had not been able to verify whether the people shown in the video were its citizens.
"Nonetheless, the Ethiopian government condemns the atrocious act," government spokesman Redwan Hussein said.
He said Ethiopia, which does not have an embassy in Libya, would help repatriate Ethiopians if they wanted to leave Libya.
In the latest video, a man dressed in black clutching a pistol stood behind some of the victims.
"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 concludes with a warning that Christians will not be safe unless they embrace Islam or pay protection money.
Image: Islamic State militants stand behind what are said to be Ethiopian Christians along a beach in Wilayat Barqa, in this still image from an undated video made available on a social media website. Photograph: Social Media Website via Reuters