Summary: 

The helicopter carrying Iranian President Ebrahim Raisi, the foreign minister, and other officials went down in a remote northern region on the way back from an official visit to Azerbaijan earlier Sunday.

It was initially described as a "hard landing" but later was widely acknowledged as a "crash" - and as the hours pass the situation looks more grim.

Search and rescue has taken hours to reach the crash site, but little is known of the progress, amid bad weather conditions.

Foreign Ministry: "Despite adverse weather and environmental conditions, efforts by rescue teams to reach the accident site continue earnestly and with hope."

Iranian population in state of 'uncertainty' as Supreme Leader asks for prayers for Raisi and the missing officials while assuring stability within government leadership.

Various countries have sent search and rescue help, including Russia and Turkey. Iran requested a night vision search and rescue helicopter from Turkey, according to Turkish disaster management agency AFAD.

Gulf countries express concern over crash, offer help in search.

'We hope for good news' Iranian official tells Al Jazeera.

Iranian official told state TV that contact was made with one of the passengers and one of the crew members of the president's helicopter on several occasions.

Press TV in follow-up cites an IRGC commander to say "Reports about contacts made by President's companions after crash not factual."

Conflicting reports: "Rescue crews haven't yet located the crash site of the helicopter carrying Iranian President Ebrahim Raisi," the head of Iran's Red Crescent Society, Pir-Hossein Koulivand, told Iranian state TV IRINN.

Islamic Revolutionary Guard Corps (IRGC) commander-in-chief Hossein Salami has arrived at the general area of the crash

"We're searching the area inch by inch, but the weather is very cold, foggy, and rainy. The rainfall is gradually turning into snowfall," said the commander of the Iranian Army's northwestern headquarters.

Heavy military presence reported in the capital of Tehran.

Thousands of Iranians pray for Raisi's safe return after crash, but there are reports of others setting off fireworks.

Raisi had been in an aging Bell helicopter, with some reports saying it was over 40 years old.

US congressman gloats over Raisi crash: "Good riddance. Raisi was a murderous human rights abuser before and during his Presidency," Rep Mike Waltz (R) wrote in a social media post.

Online speculation rampant over whether Israel or foreign intelligence could have been involved in a covert plot.

White House has been quiet but says it's aware of the developing situation; President Biden was given a briefing.