Jeh Johnson, the United States’ homeland security chief, on Sunday warned shoppers in one of America's biggest malls to be on their guard, after the Al-Shabaab terrorist group posted a video calling for attacks on western malls, AFP reports.
The warning comes as the United States and other nations are increasingly jittery about the threat of "lone wolf" attacks carried out by radicalized people in their home country.
"I would say that if anyone is planning to go to the Mall of America today, they've got to be particularly careful," Johnson said on CNN's "State of the Union" program.
The Al-Qaeda-linked Al-Shabaab group also threatened Canada's massive West Edmonton Mall, London's famous Oxford Street shopping hub and two malls in France: Le Forum des Halles and Les Quatre Temps.
A U.S. administration official said, however, there was "no indication of a specific, credible threat to the U.S."
But attacks in Paris, Copenhagen, and Ottawa by homegrown extremists have set security officials on edge, and prompted Washington to sponsor a security summit earlier this week to discuss the threat.
Al-Shabaab carried out a bloody attack and takeover of a mall in Nairobi in September 2013 that killed at least 67 people.
In the video, distributed on Twitter Saturday, the group ran a documentary-style account of the Kenya attack. It was followed by an appearance by a masked fighter who suggested similar attacks could be carried out on other malls in the United States, Canada, Britain and France.
"If just a handful of mujahideen fighters could bring Kenya to a complete stand-still for nearly a week, just imagine what the dedicated mujahideen could do in the West to American or Jewish shopping centers across the world," the terrorist in the video said, according to AFP.
"What if such an attack were to occur in the Mall of America in Minnesota? Or the West Edmonton Mall in Canada? Or in London's Oxford Street?" he said.
The video was picked up by SITE, a group that monitors jihadist websites.
The Mall of America, located in Minnesota and reputedly the country's largest with 40 million visitors a year, said it had taken extra security measures in response to the threat by the Somalia-based insurgent group.
Johnson said the threat was indicative of a new type of home-grown threat and requires careful tracking of people suspected of supporting terrorist groups.
"This latest statement from al-Shabaab reflects the new phase we've evolved to in the global terrorist threat in that you have groups such as al- Shabaab, ISIS, publicly calling for independent actors in their home lands to carry out attacks," said Johnson, who is the secretary of homeland security.
"We're beyond the phase now where these groups would send foreign operatives into countries after being trained someplace," he added.
American airstrikes in Somalia have several times targeted senior members of Al-Shabaab since the Nairobi attack.
In September, the United States killed the Somali group’s leader, Ahmed Godane, in an airstrike in Somalia.