Abbas Araghchi, Iran’s foreign minister, met with President Vladimir V. Putin in Moscow. Russia has tried to avoid entanglement in the conflict while remaining a key player in the region.

Tehran “will not hesitate in defending its people and its land,” a senior official said, after President Trump threatened to destroy Iranian power plants.

The current restrictions on the internet in Iran are coinciding with Nowruz, the observance of the Persian New Year.

Thousands of people mourned in a state-sanctioned ceremony, as people in Tehran described deepening anxiety and fear as the war continued.

The selection of a son of Ayatollah Ali Khamenei, who was killed in a strike on his compound at the start of the war, could anger Iranians seeking change.