Dhaka, July 11 -- The brutal crackdown on student-led protests in Bangladesh last year was authorised by then Prime Minister Sheikh Hasina, according to audio of one of her phone calls verified by BBC Eye.

In the 18-second audio, part of a longer 1-minute clip which was leaked online in March, Hasina says she authorised her security forces to "use lethal weapons" against protesters and that "wherever they find [them], they will shoot".

Prosecutors in Bangladesh plan to use the recording as crucial evidence against Hasina, who is being tried in absentia at a special tribunal for crimes against humanity. Up to 1,400 people died in last summer's unrest, according to UN investigators. Hasina, who fled to India, and her party reject all char...