• A 22-year-old British man, Salman Abedi, was identified as the bomber who struck a concert by the American pop star Ariana Grande at Manchester Arena, killing 22 people and injuring 59 others in the deadliest terrorist attack in Britain since 2005.

Mr. Abedi, whose parents had emigrated from Libya, died in the bombing. The Islamic State claimed responsibility for the attack, which appeared to have targeted adolescents and their families. An 8-year-old girl was among the victims.

Prime Minister Theresa May said that Britain had raised its terrorism threat level on Tuesday night to critical — the highest level — meaning that another attack may be imminent.