Sectarian violence has been on the rise in Pakistan, where radical Sunni Islamist groups often target mosques frequented by Shi'ites, whom they see as infidels.
               
"At least 20 dead bodies and more than 50 wounded people have been brought to the hospital," Shaukat Memon, a doctor at a nearby hospital, told Reuters.
               
Jundullah, a splinter group of Pakistan's Taliban, which last year pledged support for Islamic State, claimed responsibility.
               
"Our target was the Shia community (mosque). ... They are our enemies," said Fahad Marwat, a Jundullah spokesman. He did not elaborate.
               
Police said it was unclear what caused the explosion during Friday prayers in the busy central part of the town.
               
"We are trying to ascertain the nature of the blast," said Shikarpur police chief Saqib Ismail Memon. "A bomb disposal squad is examining the scene."
               
Sain Rakhio Merani, a deputy inspector general in the region, said the blast was probably caused by an explosive device, although Pakistani television quoted some residents as saying they saw a man wearing a suicide vest.
               
Part of the mosque collapsed after the explosion, burying some of the wounded in rubble. Bystanders later pulled them out, piling them into cars for the journey to hospital.
               
Pakistan has been on high alert for attacks since a Dec. 16 massacre at a school in the city of Peshawar in which at least 145 people, mainly children, were killed.
               
Shi'ites make up about a fifth of Pakistan's population of around 180 million. More than 800 Shi'ites have been killed in attacks since the beginning of 2012, according to Human Rights Watch.

Latest News from World News Desk