After his arrest late Monday, Prime Minister Cheikh Modibo Diarra appeared grim-faced on national television to announce his government’s resignation.

Nelson Mandela, 94, the former president of South Africa, has been in a hospital since Saturday, and a government statement said Tuesday that he was responding to treatment.

Three months after the attack that killed Ambassador J. Christopher Stevens, the Libyan authorities are loath to move against Islamist extremist suspects who belong to powerful militias.

The 83-year-old mother of Ngozi Okonjo-Iweala, a candidate for the World Bank’s top job last spring, was kidnapped on Sunday.

Gas and batons were used to break up a third day of demonstrations in Khartoum over the deaths of four students at a provincial university.