The attacks on Brussels and Paris were mere precursors to worse violence to be perpetrated against Europe and the West, ISIS wrote in the 14th issue of its Dabiq magazine, released online today.
"Paris was a warning. Brussels was a reminder. What is yet to come will be more devastating and more bitter," an unsigned editorial reads.
The threat comes within days of an arms cache being uncovered in Ceuta, a Spanish North African enclave that borders Morocco.
"Ceuta is a known ISIS recruiting center," a U.S. intelligence source told AMI. "The stash included pistols, sub-machine guns, edged weapons, and an ISIS flag."
It is unclear whether the cache is related to the fresh round of threats in Dabiq.
The find is "concerning," though, because Ceuta's locale on the Strait of Gibraltar offers easy access to Europe, the intelligence source said.
Europe overall is vulnerable to attack for a number of reasons, one expert told AMI.
"Europe has tight streets that go right up to large tourist areas," said Stu Bradin, a former Army Special Forces officer who was chief of staff for NATO Special Operations Headquarters in Brussels, and was Deputy Director of Operations at Special Operations Command Europe.
The streets offer direct access to targets and a challenge to pursuing law enforcement. This was a significant factor during the Brussels attacks, Bradin said. "Brussels is a rich target, and is a difficult place to navigate in terms of chasing a suspect," he said. "Traffic is a disaster. There's a lot of congestion."
Additionally, American-style security measures have not been implemented in places that accommodate large numbers of people, such as train stations or tourist hubs, he said. "If you go to Disney World they have tables out in front of the turnstiles. They have unarmed people at those tables and they make everyone open their bags and allow them to look inside. It is not a detailed search but it is a layer of protection that is done and it does not take too much effort."
Specific attack sites are not mentioned in the current issue of Dabiq. The magazine does, however, describe the threatened attacks' effects.
"Bullets and shrapnel will slash and pierce all those whom Allah’s soldiers reach," the editorial reads. "Survivors will be scarred physically and mentally, haunted whenever their eyes are closed, whenever they blink."
The threat conjures images of World War II-style devastation: "The sounds of sirens will fill the air, preceded by blasts from bombs planted in all the right places," the editorial reads. "The damage to their economy, their infrastructure, and their sources of income will make their lives harder than they now imagine."
The Spanish Interior Ministry, meanwhile, today announced the arrest of a man in selling a gun to Amedy Coulibaly, who opened fire on a kosher supermarket in Paris in 2015. Coulibaly killed a policewoman and four other people before being shot dead by police. The suspected gun seller, 27-year-old Antoine Denive, was arrested in Spain on Tuesday, the Ministry reports.
In Syria and Iraq, coalition military forces continue to strike ISIS on its claimed home turf. On April 12, the forces hit nine targets there, according to figures provided by Combined Joint Task Force - Operation Inherent Resolve.