Iranians on Thursday bid the final farewell to late president Ebrahim Raisi at the holiest site for Shiite Muslims in the Islamic Republic, in Mashhad, Iran's second-largest city.

Raisi, 63, died on Sunday alongside his Foreign Minister Hossein Amir-Abdollahian and six others when their helicopter crashed in the country's mountainous northwest.

Raisi's coffin was flown to Mashhad, in northeast Iran, after a funeral procession was held for him on Thursday morning in the eastern city of Birjand, the departed leader's hometown located in South Khorasan Province along the Afghan border. Thousands paid their respects as the coffin was driven through the streets in a motorcade.

Massive crowds had gathered for the funeral procession on Wednesday in the capital Teheran to pay their final respects to their leader.

Amir-Abdollahian was expected to be buried at the Shah Abdol-Azim shrine, a mausoleum in south Teheran.

Iran's Supreme Leader Ayatollah Ali Khamenei led prayers for Raisi, kneeling before the coffins of the eight people killed in the crash. Khamenei declared five days of national mourning and named Mohammad Mokhber, 68, as interim president until a June 28 election to choose the successor.

On Wednesday and Thursday, about 90 heads of state, government and other high-level officials from around the world attended the memorial service, Iranian media reported.

Chinese President Xi Jinping's special representative Zhang Guoqing, who attended the memorial service, also met with Mokhber.

Zhang, also a member of the Political Bureau of the Communist Party of China Central Committee and vice-premier of the State Council, expressed deep condolences over the death of Raisi and sympathy to the Iranian government and people as well as Raisi's family.

In these difficult times, the Chinese people stand firmly with the Iranian people, Zhang said, adding that he believes Iran will prevail over the temporary difficulties.

The unfortunate death of Raisi is a great loss to the Iranian people, and the Chinese people have lost a good friend, Zhang said, noting that China deeply regrets his demise.

For his part, Mokhber expressed his deep gratitude to Xi for sending Zhang as his special representative for the memorial service.

Mokhber said Iran will, as always, continue to develop relations with China and is willing to make joint efforts with China to deepen bilateral cooperation in various fields and elevate the Iran-China comprehensive strategic partnership to a new level.

Among the heads of state who attended the memorial service were Qatar's Emir Sheikh Tamim bin Hamad Al Thani, Tajikistan's President Emomali Rahmon, and Tunisian President Kais Saied, according to the Islamic Republic News Agency, or IRNA.

Turkish Vice-President Cevdet Yilmaz and Foreign Minister Hakan Fidan, Iraqi Prime Minister Mohammed Shia al-Sudani, Pakistani Prime Minister Shehbaz Sharif and Azerbaijani Prime Minister Ali Asadov also attended.

Parliament speakers from Lebanon, Algeria, Kazakhstan, Ethiopia, Mali, Russia and Uzbekistan also took part in the memorial service, paying their tributes.

Meanwhile, Iran's policy of de-escalating relations with neighbors will continue as it is an effective strategy for regional peace and cooperation, said Iranian acting foreign minister Ali Bagheri Kani, Mehr News Agency reported.

Xinhua and agencies contributed to this story.