Farnaz Fassihi has covered Iran for three decades. She was a war correspondent in the Middle East for 15 years.
Iran's top national security official, speaking on national television as the war entered a second week, said Tehran would not surrender or let up on retaliatory strikes and vowed to hold President Trump responsible for killing Ayatollah Ali Khamenei.
Ali Larijani, the head of Iran's Supreme National Security Council and a close confidant of Ayatollah Khamenei, said Iran was determined to avenge the killing of the leader, who died last Saturday on the first day of the American-Israel campaign of airstrikes against Iran. Mr. Larijani said the United States "must pay the price."
"Americans must know that we will not let them go," Mr. Larijani said. "Our people are with us, our leadership is united; there is no division in fighting Israel and America."
After the death of Ayatollah Khamenei, a three-person council comprising Iran's president, the head of the judiciary, and a jurist were placed in charge, following the constitution's directives for succession. But Mr. Larijani is widely acknowledged as Ayatollah Khamenei's preferred caretaker of the government as the top authority in national security and foreign policy.
Ayatollah Khamenei turned to Mr. Larijani earlier in the year amid nationwide protests that convulsed Iran for weeks and snowballed into a broader antigovernment movement. Iran's government crushed the protests with lethal force, killing at least 7,000 people, according to rights groups.
In his comments on Saturday, Mr. Larijani sought to reassure that Iran's leadership was united in the war effort.
Earlier in the day, some divisions appeared to surface following a video message by Iran's president, Masoud Pezeshkian. He apologized to Arab countries in the Persian Gulf for the wave of retaliatory attacks they have faced from Iran and pledged to stop. Later in the day he walked back his comments after facing criticism from hard-line elements in the Iranian government.
President Trump, however, appeared to take credit for pressuring Iran into contrition, saying in a social media post that Tehran had "surrendered to its Middle East neighbors." However, Mr. Trump added, Iran would have to surrender to him in order for the war to end, saying there would be "no deal with Iran except UNCONDITIONAL SURRENDER."
Mr. Larijani, a pragmatic veteran politician, also sought to counter the president's comments, responding to a backlash from conservatives accusing Mr. Pezeshkian of appearing weak.
Ayatollah Khamenei had sidelined the president when he authorized Mr. Larijani to take over running the country and steer it during a time of crisis in early January when protests erupted across Iran and Mr. Trump threatened military attacks.
"When the enemy attacks us from military bases in the region, we will respond; this is our right and our policy," said Mr. Larijani. "We don't want the region to be destabilized but the essence of this war will destabilize the region."
As Mr. Larijani spoke on state media, multiple explosions rocked the capital Tehran and neighboring city Karaj and residents said they could see huge balls of fire and smoke billowing in the air.
Iran's Ministry of Oil said in a statement that Israel had struck multiple oil depots belonging to the ministry in Tehran and Karaj. Israel's military confirmed the attacks.
The Islamic Revolutionary Guards Corps announced it had launched a new wave of attacks on Israel, targeting a refinery in Haifa, in retaliation for attacks on Iran's oil industry. Earlier on Saturday, Iran launched drone attacks on a hotel in Dubai's marina, a building it said belonged to Warner Brothers, and a seaport in Bahrain. The Guard said the American military was using the hotel and the seaport as logistics hubs for attacks on Iran.
Mr. Larijani said the United States waged war on Iran to split it apart and instigate civil unrest but that it had failed. He urged Mr. Trump to "accept he made a mistake and was fooled by Israel."
Devon Lum and Aaron Boxerman contributed reporting.