Speaking to the media, the minister said the names of the arrested killers could not be disclosed as an investigation is underway.
He also said some of the killers have links with political parties.
Memon confirmed that 19 people were killed and 49 injured in Thursday's bombing of a gambling den in the Ghas Mandi area.
He said that police have also arrested 85 other criminals and seized a huge cache of weapons from them.
5 killed in different shooting incidents in Karachi
In a fresh spate of violence, five people including one woman were gunned down in incidents of firing in Karachi.
Unknown men killed constable Liaqat Ali when he was going towards the police station at Hab River road. The attackers also took away his licensed rifle with them.
In Liaqatabad, unknown criminals gunned down political party activist Mohammad Shahid, while in the Mehmoodabad area 40-year-old Hanifa Bibi was killed in her house by unknown intruders.
In another incident, criminals hurled a body from a car in the Jackson area and fled from the scene. The body thrown by the criminals could not be identified.
Another man was shot down in Malir.
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