A rendition of Amazing Grace was sung in Hartford Connecticut, as the state remembered the 26 children and teaching staff killed in the Sandy Hook school massacre - one week on.
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Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.
The former shadow work and pensions secretary is considered a more viable candidate than Angela Eagle, a Labour source has told ITV News.
As many as 10 people have been rescued following the raid, according to a Bangladeshi official.