A suicide bomber attacked a crowded Sufi shrine in southern Pakistan on Thursday, killing at least 75 people and wounding dozens more in the deadliest of a wave of bombings across the South Asian nation this week.

The bomber entered the main hall of the shrine of Lal Shahbaz Qalandar in Sehwan and detonated his payload amid dozens of worshippers, according to three security officials, who said at least 20 women and nine children were among the dead.

The officials spoke on condition of anonymity because they were not authorized to brief reporters. Fazal Palejo, a senior health official in Sindh province, confirmed the toll.

Islamic State, the Middle East-based militant group which has a small but increasingly prominent presence in Pakistan, claimed responsibility for the attack, the group's affiliated news agency AMAQ reported.