Fewer foreign fighters are joining Isis - and it's making them more dangerous

US-led coalition colonel warns Isis could conduct 'high-visibility' attacks to show they are 'still viable'

As the number of Isis soldiers has fallen, there has been an increase in forced conscription and the use of child soldiers

The number of foreign fighters joining Isis has slowed for the first time, but this could result in more attacks in the West, a colonel in the US-led coalition has warned.

Fewer foreign fighters joining the militant group has contributed to a 20 per cent drop in their total military force, according to a US intelligence estimate released this month.

Using the Arabic word for Isis, Colonel Steve Warren told reporters in London: "Daesh is now beginning to lose but as we squeeze them and we begin to see them get chipped away at inside Iraq and Syria, we are going to see them look for other avenues.

Colonel Steve Warren, Baghdad-based spokesman for the US-led coalition in Iraq (AP)

"What I do know is that we have assessed that as we continue to squeeze this enemy they are going to want to show the world that they are still viable.

“One of the ways they can do that is through a high-visibility attack outside of their so-called caliphate borders.”

Up to 5,000 jihadists are feared to be in Europe after returning from terrorist training camps, according to the head of Europol, who predicted further attacks by Isis following the massacres in Paris that killed 130 people.

Colonel Warren told reporters he had no intelligence of a specific threat, but said it was something being discussed between intelligence communities in different nations.

He added: "We do not view a Paris attack or a San Bernardino attack as a sign of strength, as many have interpreted it.

"We view it as exactly the opposite.”

He also said the fall in the number of Isis fighters suggested the group was struggling to replenish its ranks after battlefield deaths and desertions.

“We’ve seen a reduction, but more of what we’ve seen is an increase in other things,” he said.

“Number one, we’ve seen an increase in forced conscription.

"Number two, we’ve seen increase in use of child soldiers, which is particularly concerning, and number three we’ve seen an increase in the use of more elite fighters in more common units.”

He warned those wanting to join the terror group they would likely be killed: “You will either be killed by your so-called partners, who have executed each other with grotesque regularity, or you will be killed by ground forces in Syria or Iraq, who don’t want you there, or - if you manage to survive either of those two things - you will be killed by coalition airpower.”