Islamic State militants are planning a takeover of Libya as a "gateway" to wage war across the whole of southern Europe, letters written by the group's supporters have revealed.
The jihadists hope to flood the north African state with militiamen from Syria and Iraq, who will then sail across the Mediterranean posing as migrants on people trafficking vessels, according to plans seen by Quilliam, the British anti-extremist group.
The fighters would then run amok in southern European cities and also try to attack maritime shipping.
The document is written by an Islamic State of Iraq and the Levant (Isil) propagandist who is believed to be an important online recruiter for the terror in Libya, where security has collapsed in the wake of the revolution that unseated Colonel Gaddafi in 2011.
The Isil propagandist, who uses the alias Abu Arhim al-Libim, describes Libya as having "immense potential" for Isil. He points out with relish that it is awash with weapons from the Libyan civil war, when large quantities of Col Gaddafi's arsenals were appropriated by rebels. Some of those weapons came from Britain, which supplied the Gaddafi regime with machine guns, sniper rifles and ammunition during his final years in power, when he was seen as an ally against Islamist terrorism.
Mr Libim also points out that Libya is less than around 300 miles from parts of the nearest European mainland.
He writes: "It has a long coast and looks upon the southern Crusader states, which can be reached with ease by even a rudimentary boat."
He also cites "the number of trips known as 'illegal immigration' from this coast, which are huge in number ... if this was even partially exploited and developed strategically, pandemonium could be wrought in the southern European states and it is even possible that there could be a closure of shipping lines and targeting of Crusader ships and tankers."
The propagandist's comments come amid growing concerns in the West about the collapse of security in Libya, which has a large diaspora population in the UK.
On Monday, Sir John Sawers, the former head of MI6, said that Britain should consider putting ground troops there to stop the country "being exploited by fanatics".
Security officials also share Isil's view about the possibility of using people trafficking boats to smuggle fighters into Europe.
Thanks to its vast, porous desert borders with Sub-Saharan Africa, Libya has long been a key operating hub for trafficking boats heading into Europe, but numbers have escalated dramatically since the collapse of the Gaddafi regime.
Italy's interior ministry estimates that at least 200,000 refugees and immigrants are poised to make the crossing from Libya to Sicily or the tiny island of Lampedusa, Italy's southernmost territory.
Last year more than 170,000 arrived in Italy by boat, including tens of thousands of Syrians fleeing the civil war in their home country.
Search and rescue efforts entered a dangerous new phase this week when an Italian coast guard vessel rescuing migrants 50 miles off the Libyan coast was threatened by smugglers armed with Kalashnikov assault rifles.
While the gang were concerned only with retrieving their boat for another smuggling trip, the incident demonstrated the potential threat were Isil to adopt similar smuggling tactics.
There are also fears that an increased Isil presence in Libya would encourage existing migrants there to flee north in far greater numbers.
Nasser Kamel, Egypt's ambassador to London, warned Britain brace itself for 'boats full of terrorists' unless action was taken in Libya. He spoke after 2,164 migrants were rescued at sea in a 24-hour period over the weekend in what has been described as an 'exodus without precedent'.
"Those boat people who go for immigration purposes and try to cross the Mediterranean ... in the next few weeks, if we do not act together, they will be boats full of terrorists also," he said.
Security in Libya has been on the slide due to the inability of the various militias that helped oust Col Gaddafi to agree a shared agenda. Its internationally recognised government is currently operating from the eastern city of Tobruk after being forced out of Tripoli by a rival government loosely allied with a range of Islamist factions.
Most of these groups do not share Isil's extremist vision, although some are believed to have links to the al-Qaeda faction that killed the US Ambassador, Chris Stevens, during an attack on a diplomatic compound in the eastern city of Benghazi in 2012.
Abu Bakr al-Baghdadi, Isil's leader, has since laid claim to Libya as part of his "Caliphate".
Whilst on the whole that remains more rhetoric than reality, support for the group in this war ravaged state is growing.
In September, Abu Nabil, an Iraqi and key leader within Isil, travelled to the country to build support for the group. His men took control of much of Derna, a traditionally conservative city in the east of the country, that is now being run according to the extremist group's strict Shariah law.
Hundreds of Libyans who had travelled to fight alongside Isil in Syria have started to return to fight for the group on home turf, residents say. They have expanded the group's influence into the east of the country, taking controlling of parts of Sirte, a former Gaddafi stronghold.
In late January, a group of gunmen invoked Isil's name in an attack on the Corinthia, a five-star hotel in downtown Tripoli, killing at least eight people.
Whilst The Telegraph cannot independently verify the identity of Mr Libim, the propagandist, analysts believe that his writing on Libya is widely read and influential online.
Mr Winter added: "In terms of the demographics of Isil support in Libya, we see a lot in common with its base of support in Iraq and Syria – many of its fighters are young, disfranchised men who have only bought into Isil's brand of Islamist zealotry because they are looking to forcibly empower themselves in the penetrating absence of the state.
"The risks Europe faces from Isil pre-eminence in Libya are substantial."
David Cameron has condemned the "barbaric" executions of the Egyptian Christians, who were kidnapped by Isil while working in Sirte. He added that he did not regret British efforts to oust Col Gaddafi, despite the threat from terrorists, insisting that it was the 'right thing to do".
President Abdel Fatah al-Sisi of Egypt called for an international coalition to defeat Isil in Libya on Tuesday, saying: "We will not allow them to cut the heads off our children".