The husband of the woman said that his wife and brothers-in-law had a heated argument which led to the incident.
SACM on Information Firdous Ashiq Awan blamed the PML-N leaders and activists for the killings.
The terrorists were involved in attacks over security forces, target killings and kidnapping for ransom.
The incident took place in Shah Faisal Colony.
The victim was identified as Hassan Abbas.
Jinnah Hospital authorities confirmed both man and woman, aged about 26, conceded three bullets each and pronounced dead at arrival
A day earlier, two rape accused, who were arrested by the police in the Komal Masih rape case, escaped from custody.
The killed terrorists were identified as Usman Ali and Waheed.
The slain militant was wanted by the authorities in several terror acts and belonged to the outlawed Tehreek-i-Taliban Pakistan (TTP).