Isis is building an "army of the poor" in its new haven in Libya by recruiting foot soldiers from Africa's poorest nations, intelligence chiefs have warned.
The terrorist group's Libyan chapter is swelling its ranks by offering cash bounties of up to US$1000 ($1526) to people from impoverished neighbouring countries such as Chad, Mali and Sudan to join. In countries where many earn less than US$2 a day, even a few hundred dollars is the equivalent of a year's salary.
Libyan officials admit they are almost powerless to stop the incomers, many of whom reach Libya using existing people-smuggling routes used by migrants heading to Europe.
Isis (Islamic State) is copying a strategy first used by Libya's late dictator, Colonel Muammar Gaddafi, who recruited thousands of mercenaries from black Africa to serve in his armies.
In much the same way, Isis' new "caliphate" in Gaddafi's home city of Sirte now has a growing number of black African fighters alongside the Iraqis and Syrians who make up its core leadership.
Colonel Muncif al Walda, a senior police officer in the nearby city of Misrata, said: "Illegal immigration is a menace because it brings and encourages foreign fighters to come and fight with Isis.
"Most of the migrants want to go to Europe, but some want to link up with Isis.
"Unfortunately, here in Libya we are right in the middle of the migration rat run."
Libyan officials spoke out as Britain and America increased their pressure on Libya's new Government to accept Western military help in tackling Isis, including 6000 Western troops on the ground in training roles.
Since establishing a foothold in Sirte a year ago, Isis is believed to have built up an army of between 2000 and 3000 fighters, turning the port city into a Libyan version of the group's Syrian stronghold of Raqqah.