Inside Iran, the abrupt postponement of a planned three days of mourning for slain Supreme Leader Ali Khamenei interrupted apparent plans to swiftly anoint Khamenei's hardliner son as his successor.
"Today is worse than yesterday. They are striking northern Tehran. We have nowhere to go. It is like a war zone. Help us," said Mohammadreza, 36, by phone from Tehran, with a shaky voice as explosions rang out from what Israel described as its latest wave of strikes on Iranian government targets.
Although some international financial markets recovered from falls earlier in the week, the economic effects of the campaign intensified, with countries around the world cut off from a fifth of global supplies of oil and liquefied natural gas.
Iran vowed to take revenge for a US torpedo attack on an Iranian warship off the coast of Sri Lanka on Wednesday, which killed more than 80 sailors.
Iran's foreign minister said the United States would "bitterly regret" the precedent it had set by sinking a ship in international waters without warning.
A commander of the Revolutionary Guards, General Kioumars Heydari, told state TV: "We have decided to fight Americans wherever they are."
The body of Supreme Leader Ayatollah Ali Khamenei, killed in the first hours of the US-Israeli air campaign in the first assassination of a country's top ruler by an air strike, had been due to lie in state in a Tehran prayer hall from Wednesday evening to launch three days of mourning.
But the memorial, expected to draw many thousands of mourners to the streets, was abruptly and indefinitely postponed shortly before it was due to begin.
In the hours before announcing the delay, Iranian officials had said they were close to naming Khamenei's successor, and that the leading candidate was his son Mojtaba, a powerful hardliner whose selection would be a strong gesture of defiance.
Iranian officials gave no reason for the postponement of the memorial but a source told Reuters it was motivated in part by fear of assassination of those attending while Israeli and US warplanes remain in the skies.
Memorial ceremonies of Shi'ite political and religious leaders, especially those seen as martyrs, are known for mass public displays of passion.
Announcing the younger Khamenei as successor during a mourning period would allow him to take power while his father's followers were on the streets, rallying support and making it more difficult for any opponents to mount a challenge.
Israel has said it would consider any replacement for Khamenei who continued hostile policies an immediate target to be killed.
Two sources familiar with Israel's battle plans said that having killed many Iranian leaders during nearly a week of strikes, Israel was now planning to enter a second phase when it would target underground bunkers where Iran stores its missiles.
Israel has said its aim is to overthrow Iran's clerical rulers.
The United States says its goal is to prevent Iran from being able to project force beyond its borders but it has also called on Iranians to rise up and seize power.
Many Iranians openly celebrated the death of the supreme leader, whose security forces had killed thousands of anti-government protesters just weeks ago in the worst domestic unrest since the era of Iran's 1979 Islamic Revolution.
State television was hacked on Thursday, airing a video of Reza Pahlavi, the exiled son of Iran's last shah who has emerged as a significant opposition figure.
"A heavy burden of destiny rests upon the shoulders of us all. And we, together, will walk this path until final victory. Long live Iran," he said.
A 25-year-old woman in Tehran who asked that her name not be used for security reasons said those opposed to the government were not yet able to take to the streets while the country was under attack, but had made their feelings clear by posting online videos of their celebrations at Khamenei's death.
"If Mojtaba takes over, he will be killed as well, so we are not concerned about it," she said.
Air raid sirens in Israel sent Israelis to shelters.
Military spokesman Effie Defrin said there had been a decrease in the number of daily missile launches from Iran, although "the threat still exists".
