Reports say the helicopter - one of three travelling in a convoy - made a "hard landing" after it got into difficulties in heavy fog in the north of the country

Interior Minister Ahmad Vahidi said rescuers were still trying to reach the site due to the difficult weather conditions

Raisi was heading to the city of Tabriz, in the north west of Iran, after returning from an Iran-Azerbaijan border area, according to local media

Let’s now take a closer look at who first vice-president Mohammad Mokhber is, as he's likely to be appointed as the interim president by Iran's Supreme Leader, who ultimately has the last say in all matters of state:

• Mokhber was elected as first vice-president after the 2021 elections that saw Raisi come to power
• The 68-year-old top diplomat is known for being close to Supreme Leader Ali Khamenei
• He will be a part of a three-person council to organise a new presidential election in the next 50 days
• Mokhber visited Moscow in October when Iran agreed to supply surface-to-surface missiles and more drones to Russia's military
• In 2010, the European Union included Mokhber on a list of individuals and entities it was sanctioning for alleged involvement in "nuclear or ballistic missile activities". He was removed two years later
• Mokhber had previously been head of Setad, an investment fund linked to the supreme leader
• In 2013, the U.S. Treasury Department added the fund and 37 companies it oversaw to a list of sanctioned entities

The names of some of those killed in the helicopter crash besides Iran's President Ebrahim Raisi and Foreign Minister Hossein Amir-Abdollahian have now been released.

The IRNA state news agency says that also on board were Ayatollah Mohammad Ali Al-e Hashem, the imam for Friday prayers in the city of Tabriz, and General Malek Rahmati, the governor of the Iranian province of East Azerbaijan.

The commander of the president's protection unit, Sardar Seyed Mehdi Mousavi, was also killed, as were a number of bodyguards and helicopter crew who have not yet been named.

President Ebrahim Raisi, Foreign Minister Hossein Amir-Abdollahian and several others are confirmed to have been killed in Sunday's helicopter crash in north-western Iran, state TV says.

• Foreign Minister Hossein Amir-Abdollahian was also killed in Sunday's crash, along with several others
• Earlier rescuers who reached the crash site in north-western Iran said there was "no sign of life" there
• The helicopter - one of three travelling in a convoy - crashed after it got into difficulties in heavy fog in the north of the country
• Raisi was heading to the city of Tabriz, in the north west of Iran, after returning from an Iran-Azerbaijan border area, according to local media
• The incident sparked a massive search operation that was hampered by bad weather conditions

Russia is sending a rescue team to Iran to help with the search for President Raisi, according to Russian state media.

RIA Novosti reports that the team includes 47 specialist rescuers, a number of all-terrain vehicles, and a helicopter.

It said the equipment was being loaded and would be flown to Iranian city of Tabriz, to which the president was travelling at the time of the accident.

“Both helicopters and rescuers are ready to carry out the most difficult tasks at high altitudes,” the agency quoted Kremlin spokesman Dmitry Peskov.

“As soon as weather conditions, namely fog, allow the search and rescue operation to be resumed, our specialists will join the efforts.”

As the search to locate President Raisi continues, Iranians have gathered for vigils on the streets of the capital, Tehran.

Pictures from Vali-Asr square in the centre of the city show people kneeling in prayer. Here's a look at some of the latest images:

From CNN's Abeer Salman

Hamas issued a statement expressing "great concern" after a helicopter carrying Iranian President Ebrahim Raisi and other Iranian officials crashed on Sunday.

Details about the crash are still murky, and Hamas expressed "solidarity" toward the president and the "brotherly Iranian people."

"In this painful incident, we express our full solidarity with the Islamic Republic of Iran, its leadership, government, and people, and we ask Allah Almighty to protect and ensure the safety of the Iranian President and his accompanying delegation, and to keep all harm away from the brotherly Iranian people," the Hamas statement reads.

The European Union says it has activated its rapid response mapping service, known as Copernicus, to help with the search for the crashed helicopter.

The Copernicus system provides mapping products based on satellite imagery.

In a post on X, Janez Lenarcic, European commissioner for crisis management, says the EU is responding to a request for assistance from Iran.

As we've been reporting, Iran's President Ebrahim Raisi was heading to the north-eastern city of Tabriz after returning from an Iran-Azerbaijan border area when the incident occurred.

Raisi had been visiting the Iran-Azerbaijan border, where he opened the Qiz Qalasi and Khodaafarin dams with his Azeri counterpart Ilham Aliyev.

Here are some of the latest images we've received of his visit earlier today.

Three rescue workers searching for the crashed helicopter have gone missing, a Red Crescent spokesperson says.

The search teams are close to the where the helicopter may have crashed, the spokesperson adds.

They say that the search operation will slow down as as the weather is expected to get "severely cold" soon, with more rain on the way.

Azerbaijan's President Ilham Aliyev says he was "profoundly troubled" after hearing reports about a helicopter crash involving Ebrahim Raisi.

Aliyev was with the Iranian president earlier today to open two dams around the Iran-Azerbaijan border.

"Today, after bidding a friendly farewell to the President of the Islamic Republic of Iran, Ebrahim Raisi, we were profoundly troubled by the news of a helicopter carrying the top delegation crash-landing in Iran," he writes on X.

"Our prayers to Allah Almighty are with President Ebrahim Raisi and the accompanying delegation".

He adds that Azerbaijan is ready to offer any assistance needed.

Earlier, a spokesperson for the Red Crescent said three of the group's rescue workers had gone missing during the search for the crashed helicopter.

The organisation has now said that none of its workers are missing.

"All official updates about rescue operation will either come from the task force in charge of these operations," a spokeswoman added.

Iran's Supreme Leader Ayatollah Ali Khamenei has just made a statement following reports President Ebrahim Raisi was involved in a helicopter crash.

He says the nation "should pray" for Raisi's health, state broadcaster IRIB reports.

"If the people of Iran do not worry, there will be no disruption in the work of the country", he adds.

We've just got in an image now of Iranian President Ebrahim Raisi in Azerbaijan earlier today, prior to the reported helicopter crash.

The MEHR news agency says the image shows Raisi before boarding a helicopter, but it is unclear if this is before or after he visited two dams on the Iran-Azerbaijan border.