At least 20people died and more than 170 were injured after a Bangladeshi air force training jet crashed into a school campus in the capital, Dhaka.

Footage from Milestone School and College in the suburb of Uttara showed a huge fire and thick smoke, after the aircraft slammed into a two-storey building.

The armed forces said in a statement on Facebook that the F-7 jet experienced a mechanical fault after taking off for a training exercise just after 13:00 local time (07:06 GMT) on Monday. The pilot was among those killed, the air force added.

More than 50 people were taken to the hospital with burns, many in critical condition, a doctor at the National Institute of Burn and Plastic Surgery said.

Many of the victims were students who had just been let out of school when the plane crashed. Seventeen of the casualties were children, the health ministry said.

The age range for students attending the school is between four and 18 years old.

A teacher at the college, Rezaul Islam, told BBC Bangla 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."

A year 10student said he had just left the building after finishing an exam when he saw the plane hit the building "right in front of my eyes". His best friend died in front of him, he said.

The pilot, Flight Lieutenant Md. Taukir Islam 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.

Images from the scene in the hours after the crash showed scores of emergency service workers sorting through charred rubble to try and find survivors, while being watched by huge crowds of onlookers who climbed on top of surrounding buildings to see.

Victims have been treated at seven hospitals across the city, the health ministry said.

At Uttara Adhunik Medical College Hospital, an on-duty doctor said most of the injured were aged between 10 and 15 years old, many suffering from jet fuel burns.

Massive crowds thronged Dhaka's National Institute of Burn and Plastic Surgery, among them families desperate for information about relatives and volunteers who had come to donate blood.

One man's eight-year-old nephew was among the students who died in the crash. "My beloved nephew is in the morgue right now," he said, his hand resting on the arm of his younger brother, the boy's father, who kept repeating: "Where is my son?"

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 X.

Bangladesh has announced a day of mourning on Tuesday, when the national flag will be flown at half-mast across the country.