Four suicide attackers infiltrated Shikarpur district's Khanpur tehsil, 470 kilometres north of Karachi, police said. Two of the attackers targeted an Eid prayer ground where one assailant blew himself up, injuring 10 people, two of whom were policemen. The other attacker fled, they said.
Two other suicide bombers targeted a Shia mosque but they were stopped at the entrance by policemen, which led to one of the attackers to blow himself up while the other was arrested.
Three policemen were injured in the attack, one of whom was critical. Last year, at least 61 people were killed in a suicide attack on a mosque in the district.
"Alert" policemen at the venues prevented huge casualties, police officer Beherdin Kehrio told reporters.
"If the policemen had not prevented these suicide bombers from entering the prayer venues there would have been largescale casualties because of the large gathering because of Eid prayers," he said.
He said the attackers at the Shia mosque were stopped by policemen as they looked suspicious and when confronted one of them detonated himself.
"The other attacker was brought down and arrested," he added.
Those injured in the blast have been admitted to hospitals in Shikarpur for treatment.
No group has immediately claimed responsibility for the attack.
Pakistan has been frequently hit by sectarian violence in recent years, most of them perpetrated by hardline Sunni Muslim groups against minority Shia Muslims.
However, Sindh is considered a relatively peaceful of Pakistan's four provinces and is highly influenced by Sufi doctrines and principles.