■ Prime Minister Theresa May announced on Tuesday night that Britain’s threat level had been raised to critical, its highest level, suggesting that another terrorist attack may be imminent.

■ The bomber who carried out the deadly attack at the Manchester Arena was identified by the police on Tuesday as Salman Abedi, 22, the son of Libyan immigrants.

■ Mr. Abedi died at the scene after detonating an improvised explosive device. The police were investigating whether he had any help.

■ Mr. Abedi had traveled to Libya multiple times, but the timing of his last trip is not known, according to a senior United States official, who spoke on the condition of anonymity.

■ The Islamic State claimed responsibility for the Monday night bombing that killed 22 people and wounded 59 others after a concert by the American pop star Ariana Grande.

■ Children and teenagers who were attending a concert were among the dead, the police said, including an 8-year-old girl. Ms. Grande was not hurt.

■ Part of the investigation led police officers in Manchester to arrest a 23-year-old man on Tuesday at a home southwest of the city center.

■ Britain’s leading political parties agreed to suspend campaigning ahead of the June 8 election out of respect for the victims of the attack.