Four people have been arrested on suspicion of facilitating a suicide bombing that killed more than 30 people on Friday, Pakistan's interior minister has said. Mohsin Naqvi stated that an Afghan national who is alleged to be the mastermind behind the attack was among those detained. Additionally, one counter-terrorism officer was killed and three more were wounded during the raids to arrest the suspects. The Islamic State group has claimed responsibility for the bombing that targeted Friday prayers at the Shia mosque in the Tarlai area, which was packed with worshippers. More than 160 people were injured in the blast, which is the deadliest in the capital for over a decade. Thousands gathered in Islamabad to mourn the victims on Saturday, with soldiers deployed for security. Prime Minister Shehbaz Sharif expressed deep grief, while President Asif Ali Zardari condemned the targeting of innocent civilians as a crime against humanity. Eyewitness accounts detail the chaos that ensued after the explosion. Naqvi also accused India of funding the attackers, while Pakistani Defence Minister Khawaja Asif suggested Afghan involvement, comments which have been rejected by the Afghan Taliban. The continued violence has drawn calls for increased security measures in Islamabad.