ISIS released a video on Sunday showing the apparent mass beheading of 21 Coptic Christians who had been kidnapped in December and January from Libya. Egypt responded hours later by bombing the terror group's camps in Libya, vowing to eliminate the jihadists' presence.
"Eight strikes have been conducted so far (in Derna). The plan is to target all IS locations in the country wherever they are," Mohamed Azazza, a spokesman for Libyan Prime Minister Abdullah al-Thinni, told BBC News. Libyan officials have been cooperating with Egypt's efforts.
Persecution watchdog groups condemned the mass killing of the 21 Egyptian Christians, which was shown in the video entitled "A Message Signed With Blood to the Nation of the Cross."
ISIS militants are seen in the video walking behind the Christians, who are wearing orange jumpsuits and kneeling on the ground.
The terror group, which has captured a number of cities in Iraq and Syria, has released numerous videos of mass beheadings in the past year. Several other Islamic extremist groups across North Africa and Egypt have aligned themselves with ISIS, which has allowed the jihadists to expand their operations.
While the identities of the 21 Christians have not been fully confirmed, International Christian Concern said that the men are believed to have been taken in two separate incidents in December and January when masked terrorists raided a housing complex in Sirte, Libya, where the Christians were living.
"The video released today once again demonstrates the incredible evil that is being perpetrated by militants loyal to the Islamic State. We mourn alongside of the families of those who have been killed, along with all Egyptians who saw their countrymen brutally killed, and with Christians around the world," said Todd Daniels, ICC regional manager for the Middle East.
"These Islamic extremists continue to claim their inspiration for their actions from their religious beliefs and have once again committed horrific violence in establishing their religious beliefs. We strongly urge the Egyptian government to act swiftly to provide protection for its citizens who remain in Libya and face continued threats if they attempt to flee the country."
ISIS has often targeted Christians in its attacks, and has told them to convert to Islam, pay a tax, or be killed for their faith in the cities it has captured.
The predominantly Islamic nation of Egypt has condemned ISIS in the past. Its military response to the beheadings targeted camps, training sites and weapon storage areas in Libya held by the jihadsts.
Egyptian President Abdel Fattah al-Sisi said that the militants are "inhuman criminal killers," and said that his country has the "right to respond" to such killings.
"Egypt and the whole world are in a fierce battle with extremist groups carrying extremist ideology and sharing the same goals," al-Sisi said, and declared seven days of national mourning for the murdered Christians.
The White House also responded to the latest beheading video, calling it "despicable" and "cowardly."
"ISIL's barbarity knows no bounds. It is unconstrained by faith, sect, or ethnicity," White House press secretary Josh Earnest said, using a different name for ISIS.
"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."
Fox News noted that Egypt has been tackling an Islamist insurgency in the Sinai Pennsula, where more militants have joined ISIS' mission and have been smuggling weapons across the border between Egypt and Libya.