President Xi Jinping expressed deep condolences on Monday over the death of Iranian President Ebrahim Raisi in a helicopter crash, saying that the Chinese people have lost a good friend who made positive efforts for consolidating and developing ties between Beijing and Teheran.

Raisi and other officials were confirmed dead early Monday after a challenging overnight search amid bad weather in northwestern Iran's East Azerbaijan Province, according to Iran's Islamic Republic News Agency. Supreme Leader of Iran Ayatollah Seyyed Ali Khamenei appointed First Vice-President Mohammad Mokhber as acting president, in line with Article 131 of the Iranian Constitution.

In a message sent to Mokhber on behalf of the Chinese government and Chinese people, Xi expressed deep sorrow over the passing of Raisi and extended sympathies to Mokhber, Raisi's family and the Iranian government and people.

Xi said that since Raisi took office as president, he had made important contributions to maintaining Iran's security and stability and promoting national development and prosperity. Raisi's unfortunate demise is a great loss for the Iranian people, the Chinese president said, adding that the Chinese people have lost a good friend.

Xi also said the Chinese government and Chinese people highly value the country's traditional friendship with Iran, while expressing hope that the China-Iran comprehensive strategic partnership will continue to be consolidated and developed with joint efforts from both sides.

The Chinese side also expressed deep condolences over the death of Iranian Foreign Minister Hossein Amir-Abdollahian, who also was killed in the crash. Deputy Foreign Minister Ali Bagheri Kani was appointed head of the international committee of Iran's Foreign Ministry, the Islamic Republic News Agency reported, citing an announcement by Iranian government spokesman Ali Bahadori Jahromi.

Raisi's helicopter crashed on Sunday in the Varzaqan region of Iran as he was returning from a ceremony to inaugurate a dam on Iran's border with Azerbaijan, Iran's Mehr News Agency reported. The bodies of those who had been aboard the helicopter were first transported to Tabriz in northwestern Iran before other arrangements were made, according to Pir Hossein Kolivand, head of the Red Crescent Society of the Islamic Republic of Iran, who oversaw the search.

Chinese Foreign Minister Wang Yi told reporters on Monday that after the crash, China provided active assistance with the search and rescue work.

"We are willing to continue to provide all necessary support to the Iranian side and believe that the Iranian government and people have the capability to overcome this difficult time," he said.

With condolences of other state leaders and heads of international organizations pouring into Teheran, Iran will observe five days of public mourning, as declared by Ali Khamenei on Monday morning.

"In this bitter tragedy, the Iranian nation lost a warm-hearted, humble and valued servant," said Iran's supreme leader in a public message.

Ali Khamenei expressed his "deep sorrow and regret" on social media platform X for what he called the "bitter news of the martyrdom of the people's President, the competent, hard-working Haj Sayyid Ebrahim Raisi, and his esteemed entourage".

Ali Khamenei also honored others who were killed in the crash, including Tabriz Friday Prayer Leader Hujjat al-Islam Ale-Hashem and "the diligent, active Foreign Minister, Mr Amir-Abdollahian".

Also expressing grief over the dead were former presidents Hassan Rouhani, Mahmoud Ahmadinejad and Mohammad Khatami.

Millions of Iranians had prayed for the safe return of Raisi from Sunday till Monday morning, only to sink in grief upon hearing of his death.

"I've been grabbed by grief," a middle-aged man in Teheran told CGTN on Monday, saying he loved the president.

Mokhber held an emergency meeting after rescue teams located the helicopter's wreckage, the Islamic Republic News Agency reported on Monday. The meeting was attended by Parliament Speaker Mohammad Bagher Ghalibaf and Iranian Judiciary Chief Gholam-Hossein Mohseni-Eje'i.

Mokhber said that as the country's system is well-established and strong, there will be no problem in the administration of the country.

Ali Khamenei also tasked Mokhber, the Parliament speaker and the judiciary chief to prepare for elections to choose a new president within 50 days.

Iran's Foreign Ministry also expressed gratitude to the international community for its concern and assistance since the helicopter went missing on Sunday afternoon. Neighboring Turkiye and Azerbaijan sent rescue teams with night-vision equipment, and Turkish drones located the site of the helicopter wreckage in mountainous forests on Monday morning amid heavy fog. More than 45 local teams were also sent to the region to help find the crash site.

Mike Gu in Hong Kong and Xinhua contributed to this story. 

Contact the writers at mojingxi@chinadaily.com.cn