But after a video from terror group Al-Shabaab calling for attacks on shopping malls in Canada, the United Kingdom and the United States, how worried should shoppers be?

Homeland Security Secretary Jeh Johnson told CNN Sunday that there's "no credible or specific evidence" suggesting a U.S. mall attack is in the works. But he warned Americans to watch out.

"If anyone is planning to go to the Mall of America today," he said, "they've got to be particularly careful."

The Minnesota mall is among those mentioned in the video the Somalia-based terror group apparently posted on Saturday. The video talks about Al-Shabaab's September 2013 attack at an upscale mall in Nairobi, Kenya, calling for similar attacks in the three Western countries. More than 60 people were killed in the Kenyan mall siege, which lasted four days.

CNN is only naming the malls that have responded publicly to the terror group's video threat.

Mall of America said it's aware that the video lists it as a potential target.

"We take any potential threat seriously and respond appropriately," the Minnesota mall said in a statement. "We have implemented extra security precautions; some may be noticeable to guests, and others won't be."

The FBI and Homeland Security issued a joint written statement saying local law enforcement and first responders have been told the agencies are not "aware of any specific, credible plot against the Mall of America or any other domestic commercial shopping center."

The police department in Bloomington, Minnesota, which regularly patrols the mall, also said there was no credible threat against it, describing the mall as a "very safe place."

"Enhanced security measures to include additional personnel have been implemented and all information is being monitored," police said in a statement Sunday.

Stressing that there is no known credible threat to any mall, Johnson also cautioned, "I won't know about when the next bad actor is going to strike."

Another U.S. law enforcement official familiar with the situation also told CNN that there is no actual working threat against any mall in the country and added that no one should avoid going to a mall because of the online threat.

A top Canadian official condemned the video , saying authorities there are monitoring threats and will take "the appropriate actions" to protect public safety.

"Canada will not be intimidated by threats from any terrorist organization," Public Safety Minister Steven Blaney said.

Bulletin to police: No indication of ongoing plot

A joint intelligence bulletin from the Department of Homeland Security and the FBI states there is no indication of an ongoing plot from Al-Shabaab in the United States, according to two law enforcement officials who have seen it.

The bulletin, sent to law enforcement around the country, urges vigilance against a lone wolf-type attack that the group's latest video message could inspire.

The intelligence assessment, the bulletin says, is that there is no credible specific threat to malls in the United States.

The Department of Homeland Security and the FBI believe the video was an attempt by Al-Shabaab to compete for attention and recruits with other terrorist groups, one official said.

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Al-Shabaab's strength is compromised, a U.S. law enforcement official told CNN, and while the group has the desire to see a mall attack in the United States, it likely doesn't have the capability to do so.

"There will be enhanced security (at malls)," Johnson said, "but public vigilance, public awareness and public caution in situations like this is particularly important, and it's the environment we're in, frankly."

A short time later, Homeland Security Assistant Secretary Tanya Bradsher told CNN that Johnson "didn't say that they should not go to the mall. He told shoppers to be extra vigilant and that security was increased."

Minnesota governor's office: We're monitoring the situation

Matt Swenson, a spokesman for Minnesota Gov. Mark Dayton, said the governor is "monitoring this situation, and will continue to consult the guidance of federal, state and local law enforcement officials, who are working together to assure the safety of all Minnesotans."

Security concerns didn't stop shoppers from packing the Mall of America on Sunday, CNN affiliate WCCO reported

Some shoppers were taking the situation in stride. Others said they were concerned about the threat.

"I'm scared, because I have kids," Brittany Segler told WCCO.

Canadian mall steps up security

The West Edmonton Mall in Alberta, Canada, which was also listed in the Al-Shabaab video, said it has implemented extra security and is working with federal and local law enforcement agencies.

Edmonton police said there was "no imminent threat" to the city, Canadian broadcaster CBC reported

"This was a very general comment ... it wasn't a specific threat," Brian Simpson, deputy chief of the Edmonton Police Service, told CBC. "However, we as a policing agency (are) absolutely paying attention to this."

In the United Kingdom, Metropolitan Police Counter Terror Command said it is aware of the Al-Shabaab video.

The FBI has a program to work with various malls around the country to improve security, the law enforcement official also told CNN.

After the 2013 Nairobi attack, the bureau worked with some malls last year to test the readiness of SWAT teams by staging fake attacks during hours when malls were closed, the official said.

Al-Shabaab's previous targets

Although Al-Shabaab has also targeted youth in Canada, Finland and the UK for recruitment, its past attacks have been limited to East Africa.

But the Somalia-based militants have heavily recruited in Minneapolis, where young men have been slipping away to join the terror group. The city is home to the largest Somali population in the United States.

In addition to Kenya and Somalia, Al-Shabaab has also struck in Uganda, where it killed more than 70 people gathered to watch a World Cup soccer match in Kampala five years ago. Kenya and Uganda have sent their forces to neighboring Somalia to battle the extremists.

As the attacks get more daring, the international community has rallied to fight the militants.

Last year, the U.S. launched an airstrike in Somalia that killed the Al-Shabaab leader. The terror group later replaced him and vowed to avenge his death.

Al-Shabaab started off with a goal of waging a war against the Somali government in an effort to implement a stricter form of Islamic law, or Sharia.

It has since shifted focus to terrorist attacks in Somalia and beyond.