Propaganda released by Isis has detailed plans to use Libya as a base to cause “pandemonium” in Europe by hijacking immigrant boats crossing the Mediterranean.

The beheading of 21 Coptic Christians on a Libyan beach last week showed Isis was on the doorstep of Europe on a second front after months of fighting along the Turkish border.

An online essay written by a prominent Isis supporter claiming to be in Libya called the country the “strategic gateway for the Islamic State” and announced the “blessed expansion” of its so-called caliphate into North Africa.

The essay, translated by counter-extremism think-tank the Quilliam Foundation, said: “(Libya) has a long coastline and looks upon the southern Crusader states, which can be reached with ease by even a rudimentary boat and note that the number of ‘illegal immigration’ trips from this coast is massive, estimated to be as high as 500 people a day, as a low estimate.

“According to many [of these immigrants], it is easily possible to pass through Maritime Security Checkpoints and arrive in cities.

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

“If this was even partially exploited and developed strategically, pandemonium could be wrought in the southern Europe. It is even possible that there could be a closure of shipping lines because of the targeting of Crusader ships and tankers.”

The essay claimed that the huge weapons stockpiles left by vying powers in Libya’s civil war as well as years of military backing by Britain, the US and others could be exploited, along with its huge tracks of desert and mountain ranges that would be difficult for foreign intelligence to survey.

“My brothers, Libya, by the permission of God, is the key to Egypt, the key to Tunisia, Sudan, Mali, Algeria and Niger too,” it continues.

“It is the anchor from which can be reached Africa and the Islamic Maghreb. However, for this dream to become a reality we must move quickly – partial commitment to the cause will not suffice.”

Libyan National Army fighters stand at the entrance of a destroyed building after clashes with Isis in Benghazi, last December (Getty Images)

Charlie Winter, the Quilliam researcher who wrote the report, emphasised that the essay must be treated as “unofficial propaganda” and could not be taken as fact, although it provided an insight into Isis’ thinking.

It was initially written in Arabic and posted in January, he said, showing it to be intended for supporters rather than just to frighten Western powers.

A spike in the number of migrants fleeing the chaos in Libya has already been seen in recent months, with Italy recording at least 2,490 people landing on its shores since Sunday.

Boat crossings from Libya can be deadly - this shoe was seen floating after one carrying 170 migrants sank in August (MAHMUD TURKIA/AFP)

Italy’s security services fear that the jihadists could take over the trafficking, the Times reported, as a source of revenue as well as to spread terror.

Migrants in Lampedusa claimed traffickers had forced them to leave Libya because of fears that Isis was planning to force them into its ranks.

“The traffickers want to get them out before that happens,” an aid worker said.

Paolo Gentiloni, Italy’s foreign minister, said after Isis captured part of the Libyan coast that Italy would be “ready to fight” the jihadists in Libya, but the Prime Minister later backtracked on his statement.

Migrants at Lampedusa told aid workers Libyan traffickers fear Isis will force them into their ranks (AFP/Getty)

Isis’ gains in the war-torn country had previously gone largely unnoticed as they gained a foothold in the coastal port city of Derna, nearby Sirte and Nofaliya last year.

Libya has been in turmoil as rival militias and governments fight for supremacy in the wake of Muammar Gaddafi’s overthrow during the 2011 Arab Spring.

Isis seems to have seized its chance in the country by uniting existing Islamist militias under its banner, recruiting rival jihadists and reportedly sending top figures including its former leader of Iraq’s Anbar province, Abu Nabil al-Anbari, to drum up support.

The group’s military gains last summer had 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.

Isis violently announced its presence in Libya with a propaganda video showing the simultaneous beheading of 21 Egyptian Coptic Christian hostages (AFP/Getty)

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

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

Days before Isis released its gory video depicting the Egyptians’ murders, 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.

“(Isis) are growing. They are everywhere,” Ali Zeidan said.

“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.