A suicide bomber blew himself up at a crowded Sufi shrine in southern Pakistan on Thursday, police said, with local media reporting at least 25 people had been killed and dozens more wounded. This was the fourth in a string of terror attacks in the country in five days.

The explosion occurred at the Lal Shahbaz Qalandar shrine in Sehwan town in Sindh province when a large number of people had gathered for ‘dhamaal’ (a Sufi ritual), Pakistani media reported.

Prime Minister Nawaz Sharif immediately condemned the attack on Lal Shahbaz Qalandar which was packed with worshippers when the bomb hit.

A suicide bomber entered the shrine as crowds massed on Thursday, a statement from the Sindh police spokesman said. It is believed the attacker made his way onto the site through the shrine’s golden gate before detonating the bomb near a window.

Local Dawn TV quoted a medical superintendent identified as Moinuuddin as saying 25 bodies and 25 seriously wounded were brought to a local hospital.

Geo TV quoted an unnamed medical official as saying at least 30 were killed.

There was no immediate claim of responsibility for the shrine blast.

On Wednesday, seven people were killed when suicide bombers targeted a van carrying judges in Peshawar and a government compound in the restive Mohmand region. Those attacks came two days after a suicide bombing in the eastern city of Lahore, the capital of Punjab province, killed 13 people and injured dozens. A faction of the Pakistani Taliban, Jamaat-ur-Ahrar, said it had carried out that attack.

Sharif in his statement decried the attack on the Sufi religious minority and vowed to fight Islamist militants who target the government and anyone who does not adhere to their strict interpretation of Sunni Islam.

“The past few days have been hard, and my heart is with the victims,” Sharif said.

“But we can’t let these events divide us, or scare us. We must stand united in this struggle for the Pakistani identity, and universal humanity.”