Tareq Abu Khdeir, speaking via a representative from the US consulate in Jerusalem who was allowed to visit him in the police station, sent a message to his parents: "I am holding up OK."
The fifteen year old, who is an American citizen and attends high school in Florida, is alleged to have been badly beaten by Israeli security forces during violent clashes in East Jerusalem on Thursday.
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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.