A Human Rights Watch report said refugees were being coerced, threatened and forced to leave Pakistan and return to war-torn Afghanistan
Save the Children said Taliban's growing influence and Pakistan's repatriation policy are key reasons for the looming crisis
No group immediately claimed responsibility for the attack, but militants such as Taliban and the Islamic State group have previously carried out similar attacks
The attack comes as the US administration contemplates whether to send more troops to rein in attacks in the war-strife country
Taliban forces have increased their attacks in the weeks before Ramzan, with a string of strikes in Kandahar, Paktia, and Helmand, among other provinces
US-Forces Afghanistan had said earlier that if confirmed, the death of the Hasib and his associates would "significantly degrade ISIS-K operations in Afghanistan and help reach our goal of destroying them in 2017."