At least 27 people were killed and 170 injured when an air force jet crashed into a school in Dhaka, Bangladesh.

In a statement on Facebook, the armed forces said the Chinese-made F-7 jet experienced a mechanical fault after taking off for a training exercise, and the pilot attempted to divert the plane to a less populated area, crashing into Milestone School and College.

According to students, the school building violently trembled, and what followed was a big explosion that sent them running for safety.

Year 10 student Farhan Hasan told the BBC he had just left the building after finishing an exam when he saw the plane crash into the building.

“My best friend, the one I was in the exam hall with, he died right in front of my eyes,” he said

The crash caused a fire that left the school building in flames.

According to officials, 171 people, mostly students, with burns were rescued and taken from the scene in helicopters, ambulances and in the arms of fire fighters and parents.

Initially, 20 deaths were reported, however, 7 others died due to the injuries overnight while receiving treatment.

20 bodies have been handed over to their families, while some of the charred bodies that were beyond recognition need DNA tests for matching.

This is the deadliest plane crash witnessed in Bangladesh following another F-7 training jet that crashed outside Dhaka in 2008, only killing its pilot who had ejected after he discovered a technical issue.