Updated 1:30 a.m. ET —
A video released Sunday showed the beheading of 21 Egyptian Coptic Christians in Libya by ISIS militants.
The video, being widely circulated on the Twitter accounts of ISIS supporters, is titled "A Message Signed With Blood to the Nation of the Cross."
Like previous ISIS beheading videos, the footage is highly edited with slick production values. It opens with the men in orange jumpsuits being led along a beach purportedly on the Mediterranean by men in black with masks.
In a message to the "crusaders," a masked man holding a knife says the group is "chopping off the heads of those that have been carrying the cross illusion."
Secretary of State John Kerry offered condolences Sunday night as Egyptian leaders considered their response to the killings.
A statement from the White House condemned the "heinous act" and called for support of United Nations' efforts to resolve conflict in Libya:
The United States condemns the despicable and cowardly murder of twenty-one Egyptian citizens in Libya by ISIL-affiliated terrorists. We offer our condolences to the families of the victims and our support to the Egyptian government and people as they grieve for their fellow citizens. ISIL's barbarity knows no bounds. It is unconstrained by faith, sect, or ethnicity. This wanton killing of innocents is just the most recent of the many vicious acts perpetrated by ISIL-affiliated terrorists against the people of the region, including the murders of dozens of Egyptian soldiers in the Sinai, which only further galvanizes the international community to unite against ISIL.
Egypt's Coptic Church released the following statement on Facebook:
The names of the slain Christians were released by the Coptic Church's Bishop Anba Ermia on Twitter, and translated into English by D.C.-based lawyer Mai El-Sadany.
British Prime Minister David Cameron condemned the video, describing it on Twitter as a "cruel and barbaric act."
The new video follows the horrific footage released by ISIS earlier this month showing the death by fire of captured Jordanian pilot Muath al-Kaseasbeh.
His brutal murder unleashed a wave of anger in Jordan, with the government promptly executing three convicted terrorists who had long been on death row.
Last week, the U.S. government confirmed the death of Kayla Jean Mueller, an American woman who died after more than a year in ISIS captivity.
UPDATE: Egyptian warplanes carried out airstrikes against ISIS targets Monday, the Associated Press reported.
The United Nations Security Council have released the following statement condemning the killings in Libya:
The members of the Security Council condemned in the strongest terms the terrorist bomb attacks against the embassies of Egypt and the United Arab Emirates in Tripoli, Libya, on 13 November.
The members of the Security Council condemned all acts of violence against diplomatic premises, which endanger innocent lives and seriously impede the normal work of diplomatic representatives and officials.
The members of the Security Council reaffirmed that terrorism, in all its forms and manifestations, constitutes one of the most serious threats to peace and security and that any acts of terrorism are criminal and unjustifiable, regardless of their motivations, whenever and by whomsoever committed.
The members of the Security Council reaffirmed the need to combat by all means, in accordance with the Charter of the United Nations and all obligations under international law, in particular international human rights, refugee and humanitarian law, threats to international peace and security caused by terrorist acts.
The members of the Security Council underlined the need to bring the perpetrators of these acts to justice.
The members of the Security Council recalled the fundamental principle of the inviolability of diplomatic and consular premises, and the obligations on host Governments, including under the 1961 Vienna Convention on Diplomatic Relations and the 1963 Vienna Convention on Consular Relations, to take all appropriate steps to protect diplomatic and consular premises against any intrusion or damage, and to prevent any disturbance of the peace of these missions or impairment of their dignity, and to prevent any attack on diplomatic agents and consular officers.