The bomb that hit the residential area was American, according to a weapons expert and a visual analysis by The Times. It killed five people and wounded 67 others, the Iranian authorities said.

China’s leader, Xi Jinping, is seeking to deepen ties with a longtime U.S. security partner and to project a larger role for Beijing in a region rocked by war.

© Pool photo by Khaled Desouki

The latest measures have forced the cancellation of English proficiency and graduate exams, isolating many Iranians most eager to foster ties with the world.

© Arash Khamooshi/Polaris for The New York Times

Experts warn that a campaign aimed at avoiding military escalation could instead provoke it, as Iranian leaders vow retaliation across the oil-rich Gulf.

© Arash Khamooshi/Polaris for The New York Times

Iran’s new hard-line national security adviser, Mohsen Rezaei, vowed to prevent “a single drop of oil” from leaving the region.

© Mohammed Salem/Reuters

Ayatollah Mojtaba Khamenei’s appointment of hard-line loyalists to top jobs suggests he is prepared to keep the country on a war footing and to quash domestic dissent.

© Arash Khamooshi/Polaris for The New York Times