A suicide bomber attacked a crowded Sufi shrine in southern Pakistan on Thursday, killing at least 72 people and wounding dozens more in the deadliest of a wave of bombings across the South Asian nation this week.

Islamic State, the militant group which has a small but increasingly prominent presence in Pakistan, claimed responsibility for the attack on the burial site of a Sufi saint, the group’s affiliated news agency Amaq reported.

Senior police officer Shabbir Sethar told Reuters from a local hospital that the death toll was likely to rise.

“At least 72 are dead and over 150 have been injured,” Mr Sethar said by telephone.

The attack on the famous Lal Shahbaz Qalandar shrine in the town of Sehwan Sharif comes as the Pakistani Taliban and other rival Islamist militant groups carry out a new offensive.

The violence has shattered a period of relative security in Pakistan, underscoring how militants still pose a threat to stability in the nuclear-armed country of 190 million people.

The high death toll in the shrine bombing makes it one of the worst attacks in Pakistan in recent years.

The bomber entered the shrine as crowds massed on Thursday, a statement from a Sindh police spokesman said.

Rescue effort

Rescue officials said dozens of wounded people were being ferried in private cars to hospitals.

Pakistan’s prime minister Nawaz Sharif quickly condemned the bombing, decrying the assault on the Sufi religious minority.

He vowed to fight Islamist militants.

“My heart is with the victims,” Mr 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.”

An ancient mystic branch of Islam, Sufism has been practised in Pakistan for centuries.

Lal Shahbaz Qalander is Pakistan’s most revered Sufi shrine, dedicated to a 13th-century saint whose spirit is invoked by devotees in ecstatic daily dancing and singing rituals in Sehwan Sharif.

Thursdays are an especially important day for local Sufis.

Most of Pakistan’s myriad radical Sunni militant groups see Sufis, Shia Muslims and other religious minorities as heretics.

Reuters