A survivor of the Kazakhstan plane crash that killed 12 people said "the roof began shrinking" after the jet collided with a concrete wall and a two-story building.

The Bek Air jet with 98 people aboard struggled to get airborne and crashed shortly after takeoff Friday after departing from Almaty, Kazakhstan's largest city and former capital, airport officials said.

"The left-wing jolted really hard, I noticed that then jolted the right. And the plane began swinging as a boat," said entrepreneur Aslan Nazaraliyev.

Exactly what caused the aircraft, identified as a 23-year-old Fokker 100, to crash remains as yet unclear.

Authorities quickly suspended all Bek Air and Fokker 100 flights in Kazakhstan pending the investigation.

Fifty-four people people were reported hospitalized with injuries, at least 10 of them in critical condition, officials said.

Government officials said the jet underwent de-icing before the flight, but Nazaraliyev recalled that its wings were covered in ice, and passengers who used emergency exits over the wings slipped and fell.

What happened?

Flight number 2100 was scheduled to fly from Almaty, a city in southern Kazakhstan, to the capital Nur-Sultan.

The Bek Air-operated aircraft took off at 7.21 am local time (2.21 am CET), according to airport authorities. The aircraft, a Fokker 100, disappeared from the radar a minute later. The alarm was raised at 7.25 am.

The plane quickly lost altitude during take-off, broke through a concrete fence and hit a two-story building, the airport said.

Kazakhstan's Deputy Prime Minister, Roman Sklyar, said there were two skid marks from the tail end of the plane on the runway, indicating it struggled to take-off. Those that died were mainly at the front of the aircraft, he added.

One survivor said the plane started shaking less than two minutes after takeoff.

"At first, the left wing jolted really hard, then the right. The plane continued to gain altitude, shaking quite severely, and then went down,'' Aslan Nazaraliyev, one of the passengers who survived the crash, told The Associated Press.

"The plane began shaking severely," he said. "It was a nightmare inside. I put my phone in the pocket and tightened up the safety belt tightly. And the plane leaned forward. It was clear that we would crash into the ground.

"The bang was strong and lights went off. Some were alive, some were not. Someone screamed that we should exit through the right side. On the right of me, there was a man. I think he opened the emergency exit. I didn't see it before and it turned out to be next to me. We began exiting through it onto the aeroplane wing."

What do we know about the victims?

There were 98 people on board, including five crews members. Twelve people died and at least 54 people were hospitalised, around 10 of them in a critical condition, officials said.

Russian media reported the injuries included cerebral, hip, and lower limb injuries.

Emergency Situations Ministry of the Republic of Kazakhstan photo via AP

Later on Friday, people were pictured leaving flowers at the airport to pay tribute to victims of the crash.

Saturday (28 December) has been declared as a national day of mourning in Kazakhstan.

What do we know about Bek Air?

Bek Air was founded in 1999 with the aim of providing VIP flights to the business community.

Today, the firm says it has become the first low-cost airline to serve a wide range of domestic destinations across the country.

Bek Air bought its first Fokker 100 in 2012 and says it now has a fleet of seven such aeroplanes.

What is Kazakhstan's air-safety record like?

In 2009, all Kazakh airlines, with the exception of the flagship carrier Air Astana, were banned from operating in the European Union because they did not meet international safety standards. The ban was lifted in 2016.

Reaction to the crash

Kazakhstan's President, Kassym-Jomart Tokayev: "Let me express my deepest condolences to the friends and families who lost their dear loved ones in the tragedy occurred on December 27. All those injured will be rendered assistance. The Government commission led by Askar Mamin was set up. All those responsible will carry severe punishment in accordance with the law."

Kazakhstan's Deputy Prime Minister, Roman Sklyar: "Today, we found two consecutive sets of skid marks from the tail end of the plane on the runway at intervals 300-400 metres, meaning the aircraft touched the runway twice while taking off. Mostly passengers who were in the front part of the aircraft died. Flight recorders have been found and have been brought for inspection."

Bek Air, the firm operating the aeroplane, said: "On behalf of Bek Air, we express our deepest condolences to the families and friends of the passengers injured in the crash of Flight 2100. For its part, the airline is doing everything possible to clarify the details of the incident as soon as possible. We sincerely grieve with everyone and share the bitterness of irreparable loss."

Social media reaction

Footage of emergency services at the crash scene. Credit: Radio Free Europe/Radio Liberty via Storyful