Iran's Supreme Leader Ayatollah Ali Khamenei on Wednesday led prayers at the funeral of late President Ebrahim Raisi and his companions, whose coffins were wrapped in Iranian flags at the University of Teheran.

After the event, Khamenei met with more than a dozen foreign heads of state and government who attended the ceremony for Raisi and other officials killed in a helicopter crash on Sunday, the Iran International Newsroom said. Iran also proclaimed five days of mourning for Raisi.

More than 40 high-ranking foreign delegates, foreign ministers, and heads of parliament were expected to take part in the commemoration ceremony in Teheran on Wednesday, Iran's semiofficial Fars news agency said.

China's Foreign Ministry spokesman Wang Wenbin said on Wednesday that Chinese President Xi Jinping's special representative Zhang Guoqing will attend the memorial service in Teheran on Wednesday. Zhang is a member of the Political Bureau of the Communist Party of China Central Committee and vice-premier of the State Council.

Qatar's Emir Sheikh Tamim bin Hamad Al Thani, Egyptian Foreign Minister Sameh Shoukry, and Kuwait's Foreign Minister Abdullah Ali Al Yahya also traveled to Teheran for the funeral.

Hamas leader Ismail Haniyeh attended the prayers on Wednesday morning.

In a speech hours before his death, Raisi emphasized Iran's support for the Palestinians.

"We believe that Palestine is the first issue of the Muslim world," Raisi said.

Russian President Vladimir Putin praised Raisi as a reliable partner always good to his word, and asked the chairman of parliament on Tuesday to convey his sympathy at memorial events.

Thousands of people, including heads of Iranian government branches and military officials, gathered at the university campus to pay their respects to Raisi and his companions.

The mourners were carrying photos of the late president, and banners, with one reading, "It is the day of mourning", while the other said, "It's an honor that I voted for a martyr".

Raisi's body was kept at Teheran's Grand Mosalla Mosque on Wednesday for the people to pay homage to the departed leader. The body will be taken to his hometown Mashhad, in eastern Iran, for burial on Thursday, IRNA reported.

In the capital, huge banners have gone up hailing the late president as "the martyr of service", while others bade "farewell to the servant of the disadvantaged".

"I was sad, I came to calm my heart and calm the heart of the supreme leader," one mourner who gave her name only as Maryam told Agence France-Presse and said she had traveled from Varamin, south of Teheran, to pay her last respects.

Details recounted

A search and rescue operation was launched at the site of the helicopter crash, with the Iranian military saying on Wednesday that domestically produced drones played a key role in locating the crash site.

On the fateful day, while returning from the inauguration of Qiz Qalasi Dam, a joint Iran-Azerbaijan project, Raisi's helicopter, which was flying along with two other helicopters, suddenly disappeared while they were trying to avoid clouds.

After the accident in the mountains, Iran's presidential chief of staff managed to contact one of the victims, Tabriz Friday prayer leader Seyyed Mohammad Ali Ale-Hashem, who succumbed hours later, according to Iranian news agencies.

In an interview with Iranian state TV, Gholamhossein Esmaili, who was traveling in one of the two helicopters in Raisi's entourage, said the helicopters were trying to avoid the clouds before the tragedy occurred.

Esmaili said the helicopters had taken off at around 1 pm local time on May 19 when the weather conditions were normal, reported IRNA.

After 45 minutes into the flight, the pilot of the president's helicopter ordered other helicopters to increase altitude to avoid nearby clouds, Esmaili said. Below them was the Dizmar forest area, nestled between the cities of Varzaqan and Jolfa in East Azerbaijan Province.

However, "after 30 seconds of flying over the clouds, our pilot noticed the helicopter in the middle had disappeared", he said.

Esmaili's pilot circled and returned to search for the president's helicopter, only to find their view affected by poor weather conditions, reported Mehr News Agency of Iran.

Several attempts to contact the president's helicopter through radio devices proved futile. The other two helicopters continued their flight and landed at a nearby copper mine.

On Tuesday, the Assembly of Experts held its first session since being elected in March.

A portrait of the departed leader was kept on the seat that Raisi would have occupied at the meeting of the 88-member panel. Acting President Mohammad Mokhber also attended.

Xinhua and agencies contributed to this story.