Pope Francis on Monday expressed “profound sadness” over the beheading of 21 Egyptian Coptic Christians by Islamic militants in Libya, saying they had been killed for their faith.

“They were executed for nothing more than the fact that they were Christians,” Francis said in impromptu remarks in his native Spanish following a meeting with John Chalmers, Moderator of the General Assembly of the Church of Scotland.

“The blood of our Christian sisters and brothers is testimony that cries out (to us),” the pontiff added.

“Be they Catholics, Orthodox, Copts, Lutherans, it does not matter. They are Christians, their blood is the same, their blood confesses (their faith in) Christ.”

The pope later called the patriarch of the Coptic Orthodox Church, Pope Tawadros II, to offer a personal message of condolence, Vatican spokesman Federico Lombardi said.

“He assured him of his prayers and tomorrow, during the funerals of the victims, he will be united in spirit with the prayer and the pain of the Coptic Church,” Lombardi said.

Egypt on Monday launched air strikes against Islamic State targets in Libya on Monday after the jihadists posted a video showing the decapitations.

The killings have been condemned around the world. They have been described as “despicable” by the United States and “barbaric” by Al-Azhar, the Cairo-based institution which is regarded as Sunni Islam’s leading theological authority.