The two gunmen Sohail Baloch alias Shooter and Sarfaraz alias Kaala opened fire at the security men as they arrived at Jahangir Road to carry out a search operation.
An exchange of fire took place between CTD personnel and the assailants in which the two gunmen were killed.
In-charge of the counter terrorism department SSP Umar Khattab has said that the slain gunmen had shot dead a CTD official Shahab Haider recently. He said that Baloch and Sarfaraz were habitual criminals who used to loot passersby at Jahangir Road and they were drug dealers as well.
The weapon, used in the killing of the CTD man, was also recovered from the slain gunmen.
Police rounded up over 21 suspects in raids across Karachi on Friday night.
Around 15 people were taken into custody in raids in Shah Faisal Colony and Alfalah Society. Three motorcycles and a pistol were seized during the raids. The arrested men were shifted to an unknown location for investigation.
Two suspects were nabbed following a police encounter in Water Pump area. Weapons and a taxi were recovered from the arrested men.
Mauripur Police arrested a gangster of Lyari identified as Shahjahan alias Bhoora, whereas Peerabad Police nabbed an alleged extortionist Shaikh Mohammad Akbar.
Police also carried out raids in New Karachi and New Town and arrested two suspects.