Crowds packed the streets of Tehran and Iran’s supreme leader, Ayatollah Ali Khamenei, performed funeral prayers on Wednesday for the country’s president, with senior officials from the Iranian-backed militant groups Hamas and Hezbollah joining the commemorations.

The presence of leaders from Hamas and Hezbollah — two key Iranian proxies in the Middle East — alongside an array of non-Western officials offered a stark illustration of Tehran’s international standing at a turbulent moment for the country.

The president, Ebrahim Raisi, 63, was killed in a helicopter crash along with Iran’s foreign minister, Hossein Amir Abdollahian, 60, and five others traveling with them on Sunday. Ayatollah Khamenei declared five days of mourning, and funeral observances began on Tuesday with a procession in Tabriz, the closest big city to the crash site in northwestern Iran. The bodies of Mr. Raisi and of the others killed were then taken to the holy city of Qom and to Tehran, the capital, ahead of Wednesday’s events.

Iran’s security forces implemented tight traffic restrictions for the city, the Tehran police chief, Col. Abdolfazl Mousavipour, told state television overnight. State television also reported that public transportation would be free on Wednesday — declared a national holiday — to make it easier for people to attend the funeral.

On Wednesday morning, state news media broadcast footage of huge crowds making their way to the University of Tehran, where the flag-draped coffins were housed in a large hall.

Ayatollah Khamenei, 85, entered with an entourage, laying down his cane in front of the coffins before performing the prayers. His words were carried on loudspeakers to crowds standing outside who bowed their heads in prayer, state media footage showed.

Mr. Raisi had been considered a potential candidate to succeed the supreme leader, who is reportedly in declining health. After performing the prayers, Ayatollah Khamenei embraced relatives of Mr. Raisi, video on state news media showed, stroking one boy’s head.

A funeral procession then got underway, with crowds thronging an open truck that carried the coffins to Tehran’s Azadi — or Freedom — Square past billboards showing a smiling Mr. Raisi. Many people carried photographs of the president; most wore black.

“If there is one thing that the Islamic Republic is truly adept at,” Ali Vaez, the Iran director at the International Crisis Group, said, it is “to organize funerals and bring its core constituents to the streets.”

“It’s a show of force aimed at showcasing the regime’s legitimacy to supporters at home and enemies abroad,” he added.

A late-afternoon ceremony drew foreign ministers from Arab nations including Saudi Arabia and Egypt.

State news media broadcast footage trumpeting the arrivals at the main Tehran airport, where a red carpet greeted the presidents of Tunisia, Kais Saied; and of Tajikistan, Emomali Rahmon. The prime minister of Armenia, Nikol Pashinyan, also made his way through, as did Syria’s prime minister, Hussein Arnous; and Pakistan’s, Shehbaz Sharif.

“The participating foreign delegates reflect the state of Iran’s relations with the outside world: low-level Western representation along with high-level participation by Iran’s neighbors and nonstate allies,” Mr. Vaez said.

Notably absent were particularly high-level officials from China or Russia, given that Mr. Raisi’s supporters had praised him with turning Iran’s policies away from the West toward more engagement with Beijing and Moscow. China sent Zhang Guoqing, a “special representative” of President Xi Jinping, to Tehran on Wednesday, while Vyacheslav Volodin, the chairman of the lower house of the Russian Parliament, appeared to be the most senior official from Moscow.

However, according to Barbara Slavin, an Iran expert and distinguished fellow at the Stimson Center, a think tank in Washington, the “fairly modest showing of heads of state” was most likely a reflection of Mr. Raisi’s political status — which was more akin to that of a prime minister than a president.

“Raisi was not the head of state — the supreme leader is,” Ms. Slavin said, adding that, as such, it “would not be appropriate” for President Vladimir V. Putin of Russia or Mr. Xi, China’s leader, to attend the funeral.

The attendees did include high-level representatives of Hamas and Hezbollah, who appeared at the commemorations on Wednesday amid chants of “Death to America” and “Death to Israel” from the crowds.

In an address at the funeral ceremonies, Ismail Haniyeh, who leads Hamas’s political wing from exile, recalled meeting with Mr. Raisi in Tehran during the holy month of Ramadan. At that meeting, Mr. Haniyeh said, Mr. Raisi emphasized Iran’s “unchangeable” commitment to the Palestinian cause, according to Iranian state media.

The presence of Mr. Haniyeh — who was later shown on state news media meeting privately with Ayatollah Khamenei — came despite the prospect of a looming arrest warrant from the International Criminal Court on allegations of war crimes and crimes against humanity. (Iran is not party to the statute that established the court.)

Hamas is a significant part of the network of proxies that Iran has developed and supported in the region. The militant group’s attack on Israel in October and Israel’s ensuing war in Gaza dramatically escalated tensions that last month pushed Israel and Iran to exchange rare direct attacks.

The Lebanese militant group Hezbollah, which on Monday commemorated Mr. Raisi as a “big brother,” sent Naim Qassem, its deputy secretary general to the funeral.

Throughout the day, state media continued to tout how foreign officials — from Sri Lanka, Qatar, Yemen, Afghanistan, Iraq, Malaysia and elsewhere — came to pay their respects, with many pausing to bow in front of the coffins, which had been set up on a low black stage behind a line of white flowers in a Tehran conference center.

The appearance of Egypt’s foreign minister was particularly noteworthy, given the decades of strained relations between Cairo and Tehran that Mr. Amir Abdollahian had worked to repair before his death.

While thousands of government supporters attended the funeral and memorial services across Iran, many Iranians who oppose the government and despised Mr. Raisi for his record of human rights violations showed apathy and some even cheered his death.

The helicopter crash left Iran without two of its highest-profile officials at a particularly fraught time. Iran’s clerical rulers are grappling with an economic crisis and widespread domestic discontent.

There are also questions about the future of Iran’s nuclear program. Tehran has produced nuclear fuel enriched to a level just short of what would be needed to produce several bombs. Days before his death, Mr. Amir Abdollahian met with the head of the International Atomic Energy Agency, Rafael Grossi, who was demanding better access to Iran’s nuclear facilities.

On Wednesday, Mr. Grossi said that Iran’s mourning period had caused a “temporary interruption” in discussions about cooperation. He told the news agency Reuters that he hoped the interruption would “be over in a matter of days.”

The commemorations will continue on Thursday, when Mr. Raisi will be buried in his hometown, Mashhad, in northeast Iran.

Farnaz Fassihi and Euan Ward contributed reporting.