Secretary of Homeland Security Jeh Johnson says he's taking seriously a call by Islamist extremists for attacks on shopping malls in the West, including Minnesota's giant Mall of America.

In an interview on CNN's State of the Union program, Johnson said a video released by the Somali-based group al-Shabab "reflects [a] new phase" in which terrorist networks publicly call "for independent actors in their homelands to carry out attacks.

"We're beyond the phase now where these groups would send foreign operatives into countries after being trained some place," he said.

At the end of a 77-minute video — focused mainly on the conflict between Kenya and Somalia and the deadly 2013 assault on a mall in Nairobi — an unidentified man hints that those sympathetic with the extremist group could hit similar targets in the West.

"If just a handful of mujahedeen fighters could bring Kenya to a complete stand-still for nearly a week, then imagine what a dedicated mujahedeen in the West could do to the American or Jewish-owned shopping centers across the world," the man said. "What if such an attack was to occur in the Mall of America in Minnesota? Or the West Edmonton Mall in Canada? Or in London's Oxford Street?"

Mall of America, in a statement released to Minnesota Public Radio, said it was aware of the threats.

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