Pakistan’s Prime Minister Nawaz Sharif promised in a televised address to take revenge against those responsible for the deadly Lahore attack, which saw 72 people killed and hundreds injured. At least 29 of the victims were children.

“Terrorists cannot dent our resolve. Our struggle will continue until the complete elimination of the menace of terrorism,” Sharif said. The Jamaat-ul-Ahrar faction of the Taliban, which once declared loyalty to the so-called “Islamic State” movement (IS) claimed responsibility for the bombing.

“Terrorists should know that failure is their fate,” he said.

Sharif is expected to beef up his crackdown on extremism in the wake of the attack after the leader of Jamaat-ul-Ahrar claimed that the organization had infiltrated the eastern city of Lahore, which is considered to be the Sharif’s power base. A spokesman from his office added that the prime minister would no longer be attending the Nuclear Security Summit to be held in Washington in coming days.

Three days of mourning were announced in Pakistan’s Punjab province while schools and other government institutions remained open. The Taliban have claimed responsibility for the attack, saying it was deliberately targeting Christians on Easter.