A Bangladeshi military training aircraft crashed into the campus of a school in Dhaka, killing the pilot and at least 19 others, mostly students, officials say.

Hundreds of students gathered outside the smouldering remains of a school in the Bangladeshi capital on Tuesday to demand answers after a military jet slammed into the campus, killing dozens of children.

A Bangladesh Air Force training fighter jet crashed into a school building in Dhaka shortly after takeoff on Monday, killing at least 20 people, mostly students, and injuring 171, in one of the deadliest aviation accidents in the country's history.