Hundreds of thousands of mourners gathered in Tehran on Saturday as Iran began days of funeral ceremonies for the late Supreme Leader Ayatollah Ali Khamenei, beating their chests in grief as his flag-draped coffin, enclosed in a glass case, passed through the capital.

Crowds also chanted calls for revenge against Israel and the United States.

The funeral for Khamenei, who led Iran for decades before being killed at 86 in a Feb. 28 airstrike during the opening phase of the Iran war, is expected to reinforce the country's ruling theocracy and bolster the authority of its new supreme leader, his son, Ayatollah Mojtaba Khamenei.

The show of unity comes as Iran seeks to strengthen its position in negotiations with the United States over a permanent end to the conflict while concerns persist that Israel could launch further military strikes.

During the ceremony, Iran's chief negotiator also warned France and the United Kingdom against pursuing joint naval patrols in the Strait of Hormuz, the strategic gateway to the Persian Gulf through which about one-fifth of the world's oil and natural gas shipments traditionally pass during peacetime.

Mourners wept at the sight of Khamenei's coffin alongside those of his family members, who also were killed in the airstrike, with some chanting, "Our word is one! Revenge! Revenge!" Some carried banners and flags, while billboards across the city bore Khamenei's image.

Crowds of men rhythmically beat their chests in mourning, a common practice at Shiite funerals.

"Imam Khamenei was our heart, our father, our everything," mourner Masoumeh Mohammadi said. "I still can't believe they martyred him. We will not rest until we avenge his death."

An outdoor stage set up at the Grand Mosalla resembled the one where Khamenei once delivered speeches at a husseiniyah in his compound in downtown Tehran. A chair like the one he used while delivering sermons, complete with a microphone on a stand and a small table beside it, sat on the stage. Hanging above it was an image of the late Supreme Leader Ayatollah Ruhollah Khomeini, who died in 1989.

Khomeini's funeral saw chaotic scenes as millions thronged his mourning ceremony and procession to the cemetery. Khamenei's death, only the second time Iran has lost a supreme leader since the 1979 Islamic Revolution, came months earlier and gave authorities more time to prepare.

On Saturday, volunteers sprayed cooling water on crowds in the summer heat while stands outside offered food and drinks. Men and women gathered separately inside the Grand Mosalla after passing through metal detectors and security screenings. Police armed with assault rifles stood guard on surrounding streets. Many others remained outside under the shade of trees because much of the city had shut down.

The caskets of his family members sat beneath Khamenei's, which had his black turban resting on top, identifying him as a direct descendant of the Prophet Muhammad. The dead included the wife of Mojtaba Khamenei, whose possible appearance at the funeral remained unclear. He reportedly was wounded in the attack that killed his father.

"We attended the funeral to show that we are all committed to defending our country and religion," said Ali Kazemi, who came from the northwestern city of Tabriz, about 530 kilometers (330 miles) from Tehran.

Iran chose July 4, the 250th anniversary of the founding of the United States, to begin the funeral. While authorities did not acknowledge the timing, crowds at the ceremony in Tehran chanted, "Death to America!" The refrain has been common in Iran since the 1979 Islamic Revolution, the U.S. Embassy takeover and the hostage crisis. They also chanted, "Death to Israel!"

"We knocked the hell out of Iran," U.S. President Donald Trump said in a speech at the same time in South Dakota in front of Mount Rushmore. "They want to settle so badly. We gave them a week off for a funeral."

The American president was not forgotten in Tehran. In the crowd at the Grand Mosalla, several mourners held a large flag reading "#KillTrump."

As the ceremony continued, Iran's chief negotiator, Kazem Gharibabadi, criticized a joint statement issued overnight by British Prime Minister Keir Starmer and French President Emmanuel Macron suggesting their militaries stood ready to patrol the Strait of Hormuz.

Control of the strait has been a major source of leverage for Iran, which has suggested it wants to charge vessels passing through it, challenging decades of international recognition of the waterway as an international passage.

"The security of Hormuz lies with the coastal states. The crisis-makers will be held accountable for the consequences of their adventurism," Gharibabadi wrote on X. "This is a serious warning."

Khamenei's body will be transported to cities in Iran and neighboring Iraq. Authorities have shut down streets, airspace and much of daily life for the mourning period, which will end Thursday when he is buried at the Imam Reza shrine in Mashhad, Khamenei's birthplace.

Authorities offered no immediate attendance estimate for Saturday's ceremony, which saw crowds cycle in and out of the Grand Mosalla and surrounding streets. Other cities across Iran also held mourning ceremonies.

On Sunday, a prayer for the dead is planned at the Grand Mosalla. On Monday, his body and those of his family members will be taken through the streets of Tehran, likely drawing large crowds.

"I am here to say goodbye to my beloved leader, Ali Khamenei," said a weeping Hananeh Mousavi, 27, who attended the funeral alongside her mother. "I never expected to see such a day. I wish I had died before this tragedy."