At least 100 people have been killed and dozens wounded in a suicide bomb attack on a shrine in Pakistan, according to police. Islamic State (IS, formerly ISIS/ISIL) has claimed responsibility for the attack.

"At least 72 are dead and over 150 have been injured," senior police officer Shabbir Sethar told Reuters, adding that the death toll is likely to rise.

Later, Rasool Baksh, a senior officer from the Sehwan police station, told local media the death toll had reached 100.

Military units are airlifting the wounded to nearby hospitals, according to Maj. Gen. Asif Ghafoor, the spokesperson for Pakistan's armed forces.

#Sehwan. Armed Forces have placed all required resources for rescue effort. Army and Rangers are doing rescue effort at site. — Maj Gen Asif Ghafoor (@OfficialDGISPR) February 16, 2017

The suicide bomber entered the Lal Shahbaz Qalandar shrine in the city of Sehwan Sharif through its golden gate, according to local authorities cited by Dawn news outlet.

At least 30 martyred in blast at Lal Shahbaz Qalandar shrine https://t.co/2kqeLM73dGpic.twitter.com/fkV32MZecO — Geo English (@geonews_english) February 16, 2017

The explosion took place at the spot where a ritual known as dhamaal was being performed.

"The blast occurred within the premises of the shrine. We have declared emergency in hospitals and are shifting the injured to nearby hospitals," Deputy Commissioner Munawar Mahesar told ARY News.

#Sehwan: #Blast near shrine of Hazrat Lal Shehbaz Qalandar oh my lord reham what going on in my country @KhanTanzila@RuhidaPTIpic.twitter.com/Aszn6g3cEr — Raza Ali Akhtar🌐 (@RazaKamboh) February 16, 2017

However, commissioner Hyderabad Kazi Shahid Parvez told The Express Tribune that the blast occurred “outside the mazar [shrine] where Golden Gate is located.”

The attacker blew himself up after throwing a grenade which failed to explode, according to the assistant superintendent of police.

#COAS directed imed assistance to Sehwan blast victims. Army /Rangers moved incl medical support. Hyderabad CMH ready to receive casualties. — Maj Gen Asif Ghafoor (@OfficialDGISPR) February 16, 2017

IS has claimed responsibility for the attack, according to the group's affiliated news agency, AMAQ, as cited by Reuters.

Pakistan's prime minister, Nawaz Sharif, has condemned the violence.

The shrine is built around a tomb of Lal Shahbaz Qalandar, a Sufi poet and philosopher. Large crowds gather at the shrine every Thursday to participate in dhamaal and prayers.

At least 37 dead in Sehwan blast, medical superintendent confirms https://t.co/B3OfX4l4HVpic.twitter.com/s9lD6YSRUK — The Express Tribune (@etribune) February 16, 2017

The blast is the latest in a series of attacks to hit the country this week.

A suicide bomber targeted a government office in the Mohmand tribal area on Wednesday, while a separate attack on the same day targeted government employees in Peshawar. Six people were killed in total.

On Tuesday, two police officers were killed while trying to defuse a bomb in Quetta.

Thirteen people were also killed in a suicide bombing at a rally in the eastern city of Lahore on Monday.