Vatican City, Feb 16, 2015 / 10:45 am (CNA/EWTN News).- On Sunday Pope Francis mourned the 21 Egyptian Christians beheaded by the Islamic State, calling them martyrs that “belong to all Christians.”

“The blood of our Christian brothers and sisters is a testimony which cries out to be heard,” the Pope said. “Their only words were: 'Jesus, help me!'”

Pope Francis made these off-the-cuff remarks in his native Spanish on Monday, one day after the release of a video from the self-proclaimed Islamic State purporting to show the grisly beheadings of 21 Coptic Christians from Egypt.

“It makes no difference whether they be Catholics, Orthodox, Copts or Protestants”, the pontiff continued. “They are Christians! Their blood is one and the same. Their blood confesses Christ.”

They were killed “only because they confessed Christ,” the Pope said. “I ask that we encourage each another to go forward with this ecumenism which is giving us strength, the ecumenism of blood. The martyrs belong to all Christians.”

Pope Francis telephoned Patriarch of the Coptic Orthodox Church, Pope Tawadros II, on Monday afternoon to show his deep participation in the sufferings of the Coptic Church following the executions. He assured him of his prayers, and said that tomorrow, the day celebrating the funerals of the victims, he will unite himself spiritually to the prayers and sufferings of the Coptic Church during the morning Eucharistic celebration.

On Monday, Egypt's military launched airstrikes against Libya in retaliation for the deaths of the Egyptian Christians, according to the New York Times.

The beheadings occurred weeks after some 20 Coptic Christians had gone missing near the coastal city of Surt, also known as Sirte, the report continues.

Many Egyptians, including Copts, travel to Libya seeking employment opportunities.

This is not the first time Egyptian Christians have been targeted in Libya. Last month, an Egyptian Christian teen and her parents were found dead in Surt.

Libyan authorities discovered the bodies of seven Egyptian Christians last February near militant-held parts of Benghazi.

Rev. John Chalmers, moderator for the Church of Scotland, was present for Pope Francis’ comments Sunday. In an interview with CNA shortly after his audience with the Pope, Rev. Chalmers said Pope Francis is a man of humility and prayer who “is feeling for those Coptic Christians who have been martyred.”

“In reflecting on that, it is clear that whatever denomination that Christians come from they are one," he said.

Throughout his pontificate, Pope Francis has frequently condemned violence against Christians in the Middle East. During his Urbi et Orbi address on Christmas Day, 2014, he called for peace in Libya, as well as in Nigeria, South Sudan, the Central African Republic, and the Democratic Republic of Congo.