Farhan Hasan had just finished an exam and left the classroom chatting to friends when a Bangladeshi air force training jet crashed into his school campus – killing at least 20 people.

“The burning plane was hitting the building right in front of my eyes,” the Milestone School and College student told BBC Bangla.

Footage from the school in a northern suburb of the capital, Dhaka shows a huge fire and thick smoke, after the aircraft slammed into a two-storey building.

More than 170 people were injured in the crash.

The armed forces said that the F-7 jet had experienced a mechanical fault after taking off for a training exercise just after 13:00 local time (07:00 GMT). The pilot, Flight Lieutenant Md. Taukir Islam, was among those killed.

Farhan, who was speaking to BBC Bangla alongside his uncle and his father, added: “My best friend, the one I was in the exam hall with, he died right in front of my eyes.

“In front of my eyes… the plane went right over his head. And many parents were standing inside because the younger kids were coming out since it was the end of the school day… the plane took the parents along with it.”

A teacher at the college, Rezaul Islam, told the BBC that he saw the plane “directly” hit the building.

Another teacher, Masud Tarik, told Reuters that he heard an explosion: “When I looked back, I only saw fire and smoke… There were many guardians and kids here.”

Hours after the crash, in a residential area which is quite densely populated, huge crowds gathered with people standing on top of buildings to get a view.

As people ran in all directions, ambulances and volunteers worked to find their way to carry the injured and many bodies out of the Milestone School and College.

At least 30 ambulances were seen moving people out.

One woman seeking information at the scene told the BBC her son had called her right after the crash, but she had not heard from him since.

More than 50 people, including children and adults, were taken to hospital with burns, a doctor at the National Institute of Burn and Plastic Surgery said.

Many families and relatives of victims were inside the hospital – including Shah Alam, the uncle of a Year 8 boy, Tanvir Ahmed, who died in the crash.

“My beloved nephew is in the morgue right now,” Mr Alam said holding on to his younger brother – Tanvir’s father – who was unable to speak.

Most of the victims inside the burns hospital are minors – most of them are between the ages of 9 and 14.

Many other members of the public came to the hospital to donate blood; while a number of politicians from the two prominent political parties Bangladesh Nationalist Party (BNP) and Jamaat-e-Islami visited.

Bangladesh’s health ministry said victims have been admitted across seven hospitals in the Dhaka; while the interim government has announced a day of mourning on Tuesday across the country, when the national flag will be flown at half-mast.

The pilot had tried to navigate the jet to a less populated area after the mechanical fault occurred, the armed forces statement said. He had only just taken off from an air force base in the capital.

An investigation committee has been formed to look into the incident, the statement added.

Muhammad Yunus, the leader of Bangladesh’s interim government, said “necessary measures” would be taken to investigate the cause of the incident and “ensure all kinds of assistance”.

“This is a moment of deep sorrow for the nation. I wish the injured a speedy recovery and instruct all authorities, including the hospitals concerned, to deal with the situation with utmost importance,” he said in a post on social media site X.