DHAKA: A Bangladeshi fighter jet crashed into a school in the capital Dhaka on Monday, killing 20 people and injuring more than 170 in the country`s deadliest aviation accident in four decades.

Many of the victims were young students who had just been let out of class when a Chinesemade F-7 BJI aircraft slammed into the Milestone School and College.

A photographer at the scene saw fire and rescue officials taking away the injured students on stretchers, while army personnel helped clear the mangled wreckage.

A military statement said 20 people were killed, including the pilot, and 171 others injured when the jet crashed following a mechanical failure.

An 18-year-old student, Shafiur Rahman Shafi, said he heard a huge blast that felt like an earthquake.

`There were two fighter planes... Suddenly one of the two planes crashed here (in the junior playground),` he recalled.

`It created a boom, which felt like a quake.

Then it caught fire; the army reached the spot later,` he added.

The private school offers education to children from kindergarten through to senior secondary.

Most of the injured were aged between eight and 14, said Mohammad Maruf Islam, joint director of Dhaka`s National Burn and Plastic Surgery Institute where many victims were treated.

The Bangladesh military said the pilot was on a routine training mission when the jet `reportedly encountered a mechanical failure`.

`The exact cause remains under investigation,` it said in a statement.

The pilot tried to divert the aircraft away from densely populated areas but, `despite his best efforts`, crashed into the two-storey school building, the military added.

The interim government of Muhammad Yunus announced a day of national mourning for Tuesday.-AFP