US Homeland Security has urged Americans to be vigilant following a terror threat to Western shopping centers, including Mall of America.

Secretary Jeh Johnson said he took the threat by the Somali-based group al-Shabab seriously.

In a video, al-Shabab urged followers to carry out attacks on shopping centers in the US, Canada and the UK.

Al-Shabab was responsible for the 2013 attack on Westgate shopping mall in Nairobi that killed 67 people.

Jeh Johnson told CNN that the threat was part of “a new phase” of terrorism in which attacks would increasingly come from “independent actors in their homelands”.

“Anytime a terrorist organization calls for an attack on a specific place, we’ve got to take that seriously,” he said.

In the video, a man with a British-sounding accent and full face covering calls on supporters of al-Shabab to attack “American or Jewish-owned” Western shopping centers.

He specifically mentions Minnesota’s Mall of America – the second-largest US shopping centre – and Canada’s West Edmonton Mall, as well as London’s Oxford Street and the UK capital’s two Westfield shopping centers.

Co-ordinates for the various targets were listed on the screen as they were described.

Both Mall of America and West Edmonton Mall have issued statements saying they were implementing additional security measures.

Minnesota is home to a large Somali population and a Minnesota man was indicted last week on charges of conspiring to support Islamic State (ISIS).

Police and security services in Canada, France and Denmark have been on high alert recently following attacks by so-called “home-grown” terrorists inspired by groups such as al-Shabab and ISIS.

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