A suspected robber was killed and a police officer injured in an exchange of fire between law enforcers and two assailants on a motorcycle in Karachi's Dalmia area on Friday.

The incident took place when two suspicious individuals on a motorcycle were asked by police to stop near Water Tank, Superintendent Police (SP) Gulshan Murtaza Bhutto told DawnNewsTV.

They, however, refused to stop and instead began firing at police and attempted to flee, the SP said. A police officer identified as Rana Arshad was injured in the firing and taken to Abbasi Shaheed Hospital.

When police returned fire, one of the assailants, Salman, was injured and succumbed to his wounds on the way to the hospital, the SP said. A 30-bore pistol and four rounds of ammunition were recovered from his possession, along with the motorcycle.

The other assailant, identified as Riaz, was arrested by police. He has 'confessed' to his involvement in the killing of a student, Asad, in Gulistan-i-Johar Block 1 on March 14, SP Bhutto said.

The official said Riaz had also confessed to his involvement in various incidents of street crime and robbery.

Police are searching for a third suspect, Nadeem, the official said. The three suspects are believed to have been part of a group of robbers that police had been attempting to track down since the murder of Asad last week.

In a 'confessional' video acquired by DawnNewsTV, Riaz is asked what happened the day of the killing. He says: "We went there that day. Salman said, 'I have a friend, Baloch. Let's go there'."

"When we went there, Salman didn't introduce us to Baloch. We went to a kiryana store, and he said we needed to commit a robbery. We looted the store and took the money. When we were leaving, a boy came and tried to take the stuff from Salman but Salman didn't let him. I don't remember if he moved forward or back. As soon as the boy started running, Salman fired at him from behind. Then we got on the bike and left," he stated.

A picture taken from a CCTV camera of Asad's killing had been circulating widely on social media since the incident with requests for information on those caught on camera killing the victim. The same picture was issued by the police today with their statement.