Meanwhile, Michael Green, chief executive of the British Council of Shopping Centers, a mall trade group, said that they work closely with police forces like Scotland Yard and would respond to warnings with appropriate measures. But they don't want to make malls like prisons.
"We have to make them welcoming," he said.
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AP Writers Adam Schreck in Nairobi, Kenya; Kay Johnson in Mumbai, India; Danica Kirka in London, Thanyarat Doksone in Bangkok; Kristen Gelineau in Sydney, Aust.; Rod McGuirk in Canberra, Aust.; Fu Ting in Shanghai; and Kelvin Chan in Hong Kong contributed to this report.