Majlis E Wahdatul Muslimeen (MWM) central leader Allama Mohammed Amin Shaheedi announced three days mourning, describing the incident a failure of the government.
He told media that the party's further course of action would be announced in a press conference later in the evening.
The Jafria Disaster Cell (JDC) demanded that the critically wounded victims be immediately shifted to Karachi for treatment.
A huge contingent of police, rangers and ambulances arrived at the scene from the nearby towns in the aftermath of the explosion.
Local resident Muhammad Jehangir told he had “felt the earth move beneath my feet” as he prayed at another mosque around 1.5 kilometres away.
An official with a national Shia organisation, Rahat Kazmi, told that up to 400 people were worshiping in the mosque when the blast struck.
Sindh Information Minister Sharjeel Inam Memon told that an emergency had been imposed at all hospitals in Shikarpur and surrounding talukas and cities. He added that provincial Chief Minister Syed Qaim Ali Shah and Sindh Health Minister Jam Mehtab Dahar have taken strong notice of the incident.
Prime Minister Nawaz Sharif, President Mamnoon Hussain, Pakistan Tehreek-e-Insaf (PTI) chairman Imran Khan and MQM chief Altaf Hussain issued condemnation messages against the incident.
