The U.S. is stepping up security around shopping malls, especially Mall of America, after Somali-based al Shabaab militants called for attacks on retail outlets in Minnesota, Canada and Britain.

Secretary of Homeland Security Jeh Johnson said on Sunday his department would meet head on the threat made by militants based in Somalia against shopping malls, including the enormous Mall of America in Minnesota.

Like Us on Facebook

On Sunday, Johnson called on shoppers at Mall of America to be careful. His advice follows a video posted by al Shabaab apparently calling for attacks on retail outlets --- particularly Oxford Street in London, the West Edmonton Mall in Canada and the Mall of America.

He said the al Shabaab call to arms is a new "phase" in the worldwide terrorist threat, in which militants such as Islamic State and al Shabaab publicly urge independent agents to carry out attacks in their homelands. The old mode of training agents abroad and sending them into a target country is over, he added.

The homeland security chief stresses that anytime a terrorist group calls for an offensive on a particular place, the U.S. government takes the threat seriously.

U.S. authorities have been worried about a possible radicalization among a big Somali community in Minnesota. Last week, a man in Minnesota was indicted on charges of conspiring to back Islamic militants State and deceiving federal agents looking into recruitment by militant groups.

State prosecutors said scores of Somali-Americans from the Minneapolis-St. Paul area have tried to travel abroad to back militant groups such as al Shabaab or Islamic State since 2007.

In a statement, Mall of America officials said they are keeping an eye on events with the aid of local, state and federal law enforcement agencies.

The mall is a big private retail establishment in Bloomington, Minnesota, with 40 million visitors annually. It puts in about US$2 billion to the economy of Minnesota, according to its Web site.

Canada's West Edmonton Mall in Alberta has more than 30 million visitors yearly while London's Oxford Street is one of the city's shopping areas, where several big department stores are located. 

TagsMall of America, Al Shabaab, terror threat, U.S., U.K., mall threat