At least 100 people were killed in a devastating suicide bomb attack at a mosque in Pakistan’s northwestern city of Peshawar on Tuesday. The attack, which also injured dozens of worshippers, is believed to be the deadliest in Pakistan since the 2014 Peshawar Army School attack.

Pakistani police have arrested several suspects in connection with the attack, and are focusing their investigation on how the bomber managed to enter the mosque.

The attack has been condemned by Pakistani officials, who have declared a national security crisis in the wake of the tragedy. Prime Minister Imran Khan said the attack was an “unspeakable crime” and offered his “deepest condolences” to the families of the victims.

The Taliban has claimed responsibility for the attack, saying it was in retaliation for the deaths of two of its commanders in a recent military operation.

Rescuers worked through the night to pull bodies from the rubble of the mosque, while survivors described scenes of chaos and horror.

The attack has sparked outrage across Pakistan and the world, with many calling for an end to the violence and a renewed effort to bring peace to the region.

The full extent of the tragedy is still unfolding, and authorities are still trying to identify all of the victims and determine the full scope of the attack.