A man fled from Mir Mohammad village in Tando Adam after killing his wife and sister for 'honour', police said on Monday.
Assistant Superintendent of Police (ASP) Taluka Tando Adam Hasan Jahangir told reporters that the police were conducting raids to arrest the suspect.
The bodies of both women have been sent to Taluka Hospital Tando Adam for post-mortem examination, ASP Jahangir added.
An FIR has yet to be registered.
The victims, according to police, had last week run away from the village to Sukkar allegedly with two men, who belonged to Mir Mohammad village as well. They were tracked down on Sunday, after which elders of the village handed them over to their suspected murderer after he promised that he would not harm them.
Scores of women in Pakistan are still being murdered by relatives for bringing shame on their family, more than a year since new laws came into force aimed at stemming the flow of 'honour killings'.
The legislation mandates life imprisonment for honour killings, but whether a murder can be defined as a crime of honour is left to the judge's discretion.
That means the culprits can simply claim another motive and still be pardoned, according to Dr Farzana Bari, a widely respected activist and head of the Gender Studies Department at Islamabad's Quaid-i-Azam University.