Iranian state media have confirmed that Supreme Leader Ayatollah Ali Khamenei was killed at his office in the Israeli-US attacks on Iran, following earlier reports of his killing by US and Israeli officials.

A 40-day mourning period for the longtime Iranian leader has been announced.

The Sunday confirmation comes after Iran’s Tasnim and Mehr news agencies initially reported that Khamenei remained “steadfast and firm in commanding the field”.

US President Donald Trump wrote in a post on his Truth Social platform earlier in the day that 86-year-old Khamenei was killed in the joint US-Israeli strikes, which began early on Saturday.

“He was unable to avoid our Intelligence and Highly Sophisticated Tracking Systems and, working closely with Israel, there was not a thing he, or the other leaders that have been killed along with him, could do,” Trump wrote.

“This is the single greatest chance for the Iranian people to take back their Country,” he said. “Hopefully, the IRGC [Islamic Revolutionary Guard Corps] and Police will peacefully merge with the Iranian Patriots.”

While Iranian authorities have long planned for the possible killing of Khamenei in the event of a war with the US and Israel, his assassination injects new uncertainty into an unfolding conflict that has already spurred concerns that fighting could escalate and expand further.

Israeli Prime Minister Benjamin Netanyahu had earlier also claimed that there were “growing signs” that Khamenei had been killed.

Additionally, the Reuters news agency, citing an unnamed senior Israeli official, had reported that Khamenei’s body had ⁠been located.

Khamenei has been Iran’s supreme leader since 1989, succeeding the founder of the post-shah Iran, Ayatollah Ruhollah Khomeini, who steered Iran’s 1979 revolution.

Barbara Slavin, a distinguished fellow at the Stimson Center in Washington, DC, told Al Jazeera that Iran “has a plan” in place in the event that Khamenei’s death is confirmed.

“There will probably be a council that will be set up to run the country. It may already have been running the country, as far as we know,” she said.

Trump signals continued strikes

Saturday’s strikes on Iran targeted 24 provinces, killing at least 201 people, according to Iranian media reports, citing the Red Crescent.

Among the attacks, Israel struck two schools in Iran, killing at least 108 people at the Shajareh Tayyebeh girls’ elementary school in the southern city of Minab, and two others at a school east of the capital, Tehran.

Netanyahu said in his address that many “senior figures” had been “eliminated” in the wave of attacks targeting senior leaders, as Trump called for the government to be toppled.

Israel, Netanyahu said, had killed “commanders in the Revolutionary Guard and senior officials in the nuclear programme. And we will continue.”

Trump indicated on his Truth Social post that “heavy and pinpoint bombing” of Iran would go on “uninterrupted throughout the week or, as long as necessary”.

Iran’s counterattacks on Saturday triggered air-defence interceptions in several countries where airbases with US assets are hosted, including Kuwait, Qatar, the United Arab Emirates and Bahrain.

On Saturday evening, the Iranian Revolutionary Guard Corps (IRGC) said that the third and fourth waves of “retaliatory” strikes on US and Israeli positions were ongoing, according to a statement carried by the IRNA news agency.

Guterres calls for de-escalation

United Nations Secretary-General Antonio Guterres told an emergency meeting of the Security Council that he deeply regretted that an opportunity for diplomacy had been “squandered”.

“Military action carries the risk of igniting a chain of events that no one can control in the most volatile region of the world,” he told the 15-member body. “I call for de-escalation and an immediate cessation of hostilities”.

Addressing the Security Council, Iran’s UN ambassador, Amir Saeid Iravani, said the US and Israel had “initiated an unprovoked and premeditated aggression”, attacking “civilian populated areas in multiple large cities of Iran, where millions of people reside”.

“This is not only an act of aggression, it is a war crime, and a crime against humanity,” he said.

China’s UN ambassador, Fu Cong, said Beijing was very concerned by “the sudden escalation of regional tensions”.

Russia’s ambassador, Vassily Nebenzia, condemned the US-Israeli air strikes, demanding that the US and Israel “immediately cease their aggressive actions”.