More than 70 people were killed in a suicide bomb blast at Lal Shahbaz Qalandar Shrine in Sindh, Pakistan on Thursday night. At least 300 people were injured. A suicide bomber blew himself up in the crowded area where a Sufi ritual, dhamaal, was being performed after evening prayers, Dawn reported. The bomber had blown himself up after throwing a grenade that had not exploded.

The Islamic State claimed responsibility for the explosion.

Inspector General Police (Sindh) AD Khawaja told Dawn that many of the injured were in critical condition. “They will be shifted to Karachi as soon as navy helicopters and the C-130 plane reach the nearest airport,” he said.

Prime Minister Nawaz Sharif and Pakistan’s Army Chief General Qamar Javed Bajwa were among the first to condemn the attack. The United Nations, European Union and United States have also done so. Pakistan also closed its border with Afghanistan, effective immediately.

In a statement after the attack, General Qamar Javed Bajwa appealed to the nation to stay calm.

There has been a rise in explosions in Pakistan recently – this is the fifth explosion in the country in the past week. On Monday, at least 10 people died in an explosion outside the Punjab Assembly, while on Thursday, there were two attacks in which at least two people were killed.