Police officials said that militants threw hand grenades at the mosque before raiding the building and opening fire on worshippers. Over 50 people were also injured, according to local media reports.
Eyewitnesses claimed that at least three attackers -- one of whom blew himself up -- entered the Imamia Masjid (mosque) during Friday prayers, wearing suicide vests.
At least 100 people were believed to be inside the mosque when the explosion occurred, according to a report by The Express Tribune, a Pakistani newspaper.
The attack comes less than two weeks after more than 60 people were killed in a blast inside a Shia congregation hall in the Shikarpur district of Sindh province.
Militants of the Pakistani Taliban have claimed responsibility for today’s attack.
In a statement accessed by The Express Tribune, Mohammad Khorasani, a spokesperson for the Tehreek-e-Taliban Pakistan (TTP) terrorist group, said that the attack was revenge for the execution of “Dr Usman.” Usman, a former Pakistani army soldier, was hanged in December after being found guilty of involvement in an attack on the Pakistani army’s headquarters in Rawalpindi in 2009.
Several extremist militant groups, including al Qaeda and the Taliban, have frequently targeted Shia Muslims.