A man was killed and four others were injured in a blast in this southern Pakistani port city on Monday.
The explosion occurred in Malir area of Karachi at a unit that makes cement blocks used in constructing houses.
Police said the explosive device was hidden in a cement block.
"The shop was closed for three days due to Muharram and the blast took place this morning," senior police official Raja Umar said.
The bomb comprised 1 kilogramme of explosive material including ball bearings, nut and bolts.
One of the four injured men was in a critical condition, officials at Jinnah Hospital said.
Rescue teams took the injured to hospital while a bomb disposal squad swept the area.
Police officials said the bomb was apparently planted on Sunday to target a Shia procession.
Security forces cordoned off the area and prevented the public and media from approaching the site of the blast.
In one incident, a low intensity bomb went off in Gulistan-e-Jauhar but a second one found nearby was diffused by the bomb disposal squad on Sunday night.
The bomb planted near Amroha Society gate in Gulistan-e-Jauhar went off with a loud bang but bomb disposal squad experts found another low intensity bomb near the blast site and diffused it.
On Sunday, police also claimed to have killed a terrorist and uncovered large amounts of explosive material and suicide jackets after a raid in Mangophir.
Residents said that police had also taken away some suspects to an undisclosed location.