WASHINGTON - U.S. Homeland Security Secretary Jeh Johnson is appealing for public vigilance following the release of a video purportedly by the Somali-based al-Shabab terrorist group calling for attacks on Western shopping malls. Johnson said the latest video underscores the fact that the global terrorist threat has entered a new phase.

The U.S. Homeland Security Department says it is not aware of any specific, credible plot against the Mall of America in Bloomington, Minnesota or any other domestic commercial shopping center.

The statement follows release of a video late Saturday purportedly by the al-Qaida-linked, Somali-based al-Shabab terrorist group, which calls for attacks on Western shopping malls. The group claimed responsibility for the September 2013 attack on Nairobi’s Westgate mall in which 67 people died. The masked narrator spoke of that attack at length.

"If just a handful of mujahedin fighters could bring Kenya to a complete standstill for nearly a week, then imagine what a dedicated mujihad in the West could do to the American or Jewish-owned shopping centers across the world. 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? Or any of the hundred or so Jewish-owned Westfield shopping centers dotted right across the Western world," said the narrator.

He warned of more attacks in Kenya following the country’s military operations against al-Shabab in neighboring Somalia. The authenticity of the video could not be independently verified.

Secretary Johnson, appearing on the NBC program “Meet the Press” Sunday, said new groups like Islamic State (IS) are joining al-Qaida in effectively using videos, publications, social media and the Internet to reach into communities in other countries and inspire independent actors to commit acts of violence.

"We’ve got to be vigilant. So, we ramp up security. There was a call for an attack on locations in Canada and Europe. And so, in response to that, I ramped up the presence of the Federal Protective Service at federal buildings a couple of months ago. I’m sure security at this particular mall will be enhanced in ways visible and not visible. But, it also involves public vigilance and public awareness. If you see something, say something has to be more than a slogan," said Johnson.

The Mall of America, near a sizeable Somali-American community, said it has taken extra security precautions in response to the video.

U.S. federal prosecutors Thursday indicted a Minnesota man for allegedly providing support for Islamic State and lying to federal authorities in a terror investigation.  Nineteen year-old Hamza Naj Ahmed, along with three others, was arrested in November after allegedly attempting to travel to Syria via Turkey.

Canadian police Sunday said their investigation has uncovered no imminent threat from al-Shabab. Edmonton Deputy Police Chief Brian Simpson said the West Edmonton Mall has an impressive security system that adapts to the changing environment. He also said police are closely working with the Somali and Muslim communities to identify and contain emerging threats.

"Our best opportunity to deal with like-type threats is to involve our communities, particularly with the lone wolf (individual) is where the community can definitely provide us with a lot of support and help, by identifying that behavior of radicalization. That’s our best and quickest opportunity to intervene and put it to the right place. We need to do our normal day-to-day business. That’s how we effectively deal with this. We don’t give them (terrorists) more power than they deserve, because they are terrorists and they are trying to create terror," said Simpson.

Terrorism analyst Luke Howie of Australia’s Monash University said shopping malls are obvious “soft” targets for terrorists because of their open and free spaces with no security checkpoints, in contrast to airports. By their very nature, he said, they are difficult to secure, and that makes the latest threat something to be taken seriously.

"A group like al-Shabab, they release a video for its propaganda benefit, and it’s to try and tap into that lone-wolf person, that person sitting as their computer getting radicalized wanting to act out.  And so, the propaganda potential of a video like this always, I think, needs to be taken very seriously.  So whilst, indeed, there might not be any specific intelligence that indicates there might be an attack imminent, a statement like this, a video like this from al-Shabab, or any other terrorist organization, can start to stir the pot if they have sympathizers in a particular area," said Howie.

Howie said al-Shabab initially made headlines capturing territory. Now, like other terrorist groups, they have recognized the propaganda value of using social media to export their message and gain a celebrity-like status.

Secretary Johnson said Muslim-American groups tell him terrorist organizations like Islamic State (IS) are attempting to hijack Islam. He said to refer to them as Islamic extremists dignifies them and gives them a place in the Islamic religion they do not deserve.