The US homeland security chief said on Sunday he takes seriously an apparent threat by Somali-based Islamist militants against prominent shopping sites in the West including the Mall of America in Minnesota and urged people there to be careful.
Homeland Security Secretary Jeh Johnson was reacting to a video attributed to al-Shabaab appearing to call for attacks on Western shopping areas, specifically mentioning Mall of America, the West Edmonton Mall in Canada, London's Oxford Street and sites in Paris.
Mall of America and West Edmonton Mall issued statements saying they were implementing extra security measures.
"This latest statement from al-Shabaab reflects the new phase we've evolved to in the global terrorist threat, in that you have groups such as al Shabaab and ISIL publicly calling for independent actors in their homelands to carry out attacks," Johnson told the CNN programme "State of the Union," using an acronym for the militant group Islamic State.
Staff Sergeant Brent Meyer of Canada's Royal Canadian Mounted Police said authorities are looking into the video but "there is no evidence at this time of any specific or imminent threat to Canadians." A spokesman said London police were aware of the video and were assessing it.
Asked about the threat to Mall of America, one of the world's largest shopping complexes, Johnson said: "Anytime a terrorist organisation calls for an attack on a specific place, we've got to take that seriously." He advised people going to the Mall of America to be particularly careful.
Minnesota is home to a sizeable Somali population. US law enforcement officials have been concerned about the potential for radicalisation among some of the community.
A Minnesota man was indicted last week on charges of conspiring to support Islamic State and lying to federal agents investigating recruitment by militant groups.
Prosecutors said dozens of people from the Minneapolis-St. Paul area, many of them Somali-Americans, have travelled or attempted to travel overseas to support groups such as Islamic State or al-Shabaab since 2007.
"I'm very concerned about the serious potential threat of independent actors here in the United States. We've seen this now in Europe. We've seen this in Canada," Johnson said.
Mall of America is a large private mall in Bloomington, Minnesota, that has about 40 million visitors a year, and contributes nearly US$2 billion in annual economic activity to the state of Minnesota, according to its website.
The West Edmonton Mall in Alberta, Canada, gets about 30.8 million visitors a year and has the world’s largest parking lot, according to its website. Oxford Street is one of London's busiest shopping areas, home to several large department stores.
Al-Shabaab claimed responsibility for an attack on a high-end Westgate shopping mall in Nairobi, Kenya in 2013 that killed 67 people, raising fears about the safety of malls around the world.
Security officials in Canada have been on alert in the wake of two attacks by Muslim converts last year including a gunman who attacked Canada's Parliament in October, fatally shooting a soldier at a nearby war memorial.
Inside the Mall of America on Sunday, where there were no visible signs of enhanced security, Nick Disbrowe, 23, said he was not entirely surprised when told about the videotape released by al-Shabaab. "If anyone is going to target anything, it's the Mall of America," he said.