The beheading of 21 Coptic Christians on a beach in Libya has brought Isis to the doorstep of Europe.

The mass murder, which provoked a volley of Egyptian air strikes on the group’s Libyan stronghold of Derna, realised long-held fears of militants reaching the Mediterranean coast.

Isis started in Iraq and now controls swathes of adjoining Syria, including along the Turkish border, as part of its so-called Islamic State.

Its ideology has spread much further, with pledges of allegiance from terrorist groups in Egypt, Gaza, Jordan, Lebanon, Saudi Arabia, Tunisia, Yemen and now Libya.

Days before Isis released its gory video depicting the Egyptians’ beheadings, Libya’s former Prime Minister warned that the group would soon reach the Mediterranean and even Europe if order was not restored in the country.

Ali Zeidan said Libya’s fractured government and easy access to weapons seized during the fall of Colonel Gaddafi made it more susceptible to the activities of jihadists, according to The Times.

“(Isis) are growing. They are everywhere,” he added.

In pictures: Coptic Christians mourn victims of Isis beheadings Show all 15 1 /15 In pictures: Coptic Christians mourn victims of Isis beheadings In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Egyptian Coptics mourn for the 21 men murdered by Isis AP In pictures: Coptic Christians mourn victims of Isis beheadings Egypt A man is comforted by others as he mourns over Egyptian Coptic Christians who were captured in Libya and killed by militants affiliated with the Islamic State group, outside of the Virgin Mary church in the village of el-Aour, near Minya, 220 kilometers (135 miles) south of Cairo In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Women mourn over Egyptian Coptic Christians who were captured in Libya and killed by Isis militants In pictures: Coptic Christians mourn victims of Isis beheadings Egypt A relative of one of the Egyptian Coptic Christians purportedly murdered by Isis reacts after hearing the news in the village of Al-Awar in Egypt's southern province of Minya In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Relatives of Egyptian Coptic Christians purportedly murdered by Isis militants in Libya react after hearing the news in the village of al-Awar in Egypt's southern province of Minya In pictures: Coptic Christians mourn victims of Isis beheadings Egypt President Abdel Fattah al-Sisi offers his condolences to some of the Coptic families AFP In pictures: Coptic Christians mourn victims of Isis beheadings Egypt The Grand Imam of Al-Azhar, Sheikh Ahmed al-Tayeb (R) offers his condolences to Egypt's Coptic Pope Tawadros II at Saint-Mark's Coptic Cathedral in Cairo's al-Abbassiya district In pictures: Coptic Christians mourn victims of Isis beheadings Egypt A Coptic clergyman shows a picture of a man whom he says is one of the Egyptian Coptic Christians purportedly murdered by Isis militants in Libya, during a memorial ceremony in the village of al-Awar in Egypt's southern province of Minya In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Relatives of Egyptian Coptic Christians murdered by Isis militants in Libya wlak through the village of Al-Awar in Egypt's southern province of Minya In pictures: Coptic Christians mourn victims of Isis beheadings Egypt A family relative of abducted Coptic Christian weeps AP In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Men mourn over Egyptian Coptic Christians who were captured in Libya and killed by militants affiliated with the Islamic State group, inside of the Virgin Mary Church in the village of el-Aour, near Minya, 220 kilometers (135 miles) south of Cairo In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Men mourn over Egyptian Coptic Christians who were captured in Libya and killed by militants affiliated with the Islamic State group, inside the Virgin Mary Church in the village of el-Aour, near Minya, 220 kilometers (135 miles) south of Cairo In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Protesters hold placards during a demonstration against the killing of Egyptian Coptic Christians by militants of the Islamic State in Libya, in Cairo In pictures: Coptic Christians mourn victims of Isis beheadings Egypt Egyptians protest what they characterise as Government inaction in reaction to the kidnapping of Copts in Libya, Cairo EPA In pictures: Coptic Christians mourn victims of Isis beheadings Egypt A Coptic Christian woman prays for the release of 21 Coptic Egyptian men AP

“In Libya, the situation is still under control. If we leave it one month or two months more I don’t think you can control it.

“It will be a big war in the country and it will be here in Europe as well.”

Libya has seen fierce fighting between rival militias since Gaddafi was overthrown during the 2011 Arab Spring.

Mr Zeidan, who fled to Europe after losing a parliamentary vote of confidence, reported that Isis had a growing presence in some of the bigger cities and was trying to recruit fighters from rival Islamist groups.

Libya's former Prime Minister Ali Zeidan warned that Isis would reach the Mediterranean (MAHMUD TURKIA/AFP/Getty Images)

Aref Ali Nayed, Libya’s ambassador to the United Arab Emirates, also said Isis’s presence in Libya was increasing “exponentially”.

Its military gains last summer sparked a rush by other Islamist groups in the Middle East and North Africa to ally themselves with the group by pledging allegiance and changing their names.

The jihadists behind the beheadings in Libya call themselves the Tripoli Province of the Islamic State.

Egyptians protest what they characterise as Government inaction in reaction to the kidnapping of Copts in Libya, Cairo, Egypt, 13 February 2015 (EPA)

As the turmoil in Libya continued last year, they gained control of the port city of Derna and nearby Sirte, where Isis seized the murdered Coptic hostages in December and January.

The location of their murders could not be confirmed but footage showed them dressed in orange jumpsuits kneeling on a beach. Behind each of them were masked militants who wielded their knives to kill the bound hostages simultaneously.