Mohammad Aslam Khan, head of Karachi counter-terrorism cell, told the BBC that the attack was "clearly targeted" at the Bohra Ismaili Shia community, from which most of the dead and injured came.

BBC: Pakistan attacks: Bombs strike Quetta and Karachi

This is a highly sensitive business, the number of companies around the world that have the technology to produce this kind of cell is very limited and by us going out on the BBC and explaining where our source is is equivalent to commercial suicide.

BBC: Stem cell treatment warning

Speaking from his cell ahead of the sentence, he told the BBC his worst fear was being hanged but he also dreaded life imprisonment "in one of the worst jails in the world".

BBC: Danny Fitzsimons says 'only God' can judge him