Ed Miliband has paid tribute to Labour MEP candidate Del Singh, who died in a suicide bombing at a restaurant in Kabul.
The Labour leader said he was "appalled and shocked by this barbarous act of terror".
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The hashtag #RoomForManchester was being widely shared.
Witnesses reported hearing a "huge bang" at the venue during the concert on Monday evening.
ITV News travels to Britain's eastern-most city to gauge how the electorate will be casting its votes.