Christian hostages beheaded in Islamic State video

William M. Welch | USA TODAY

Show Caption Hide Caption Christian hostages reportedly beheaded in Islamic State video A video released by the Islamic State purportedly shows militants beheading Christian hostages. There is speculation that these 21 detainees are Egyptian Coptic Christians that were kidnapped weeks ago.

Egypt has begun airstrikes against Islamic State targets in Libya hours after militants released a video purporting to show the mass beheading of Egyptian Christian hostages.

The strikes were announced Monday on state radio by a spokesman for the country's Armed Forces General Command.

Weapons caches and training camps were targeted.

The strikes were to "avenge the bloodshed and to seek retribution from the killers. Let those far and near know that Egyptians have a shield that protects them," the radio statement said.

It is the first time Egypt has publicly acknowledged taking military action in Libya.

On Sunday, a video purporting to show the mass beheading the hostages by militants in Libya claiming loyalty to the Islamic State group.

The video shows a line of men dressed in orange jumpsuits forced onto their knees and beheaded.

The video was posted on social media. On Twitter, several accounts distributed links to the video carrying the title, "A Message Signed With Blood To The Nation Of The Cross."

The Egyptian government and the Coptic Church based in Egypt both declared the video authentic. Egypt banned all travel to Libya by its citizens in response.

The Egyptian government declared a seven-day mourning period, and President Abdel Fattah al-Sisi addressed the nation late Sunday night, the Associated Press reported.

"These cowardly actions will not undermine our determination" Sisi said, according to the AP. "Egypt and the whole world are in a fierce battle with extremist groups carrying extremist ideology and sharing the same goals."

Militants in Libya had been holding 21 Egyptian Coptic Christians hostage for weeks, threatening them with death. The makers of the video identify themselves as the Tripoli Province of the Islamic State group — the Islamic militant group that controls about a third of Syria and Iraq.

Egypt's state news agency MENA quoted the spokesman for the Coptic Church as confirming that 21 Egyptian Christians believed to be held by Islamic State were dead, Reuters reported.

The Coptic Church in a statement called on it followers to have "confidence that their great nation won't rest without retribution for the evil criminals."

Why ISIS targeted Egypt's Coptic christians A new video from ISIS shows the mass beheading of 21 Egyptian Christians who were recently kidnapped in Libya. Video provided by Newsy

In the video, men in orange jumpsuits are shown being led along a beach, each accompanied by a masked militant, AP reported. The men are made to kneel and one militant, dressed differently that the others, addresses the camera in English.

"All crusaders: Safety for you will be only wishes, especially if you are fighting us all together. Therefore we will fight you all together," he said. "The sea you have hidden Sheikh Osama Bin Laden's body in, we swear to Allah we will mix it with your blood."

The men are then laid face-down and simultaneously beheaded. The militant speaker then pointed northward and said, "We will conquer Rome, by Allah's permission."

Qalini Sanyout, whose two nephews were among the hostages, answered the phone Sunday night amid the sound of wailing in the background.

"What can we say? Can someone tell us if this is true." he said repeatedly, AP reported. "The whole village is in mourning. Men are covering their heads with dust and mud."

Thousands of Egyptians have traveled to neighboring Libya in search of jobs since an uprising at home in 2011, despite dangerous conditions.

Contributing: The Associated Press