The victims in the overnight drive-by shootings and other acts of violence in different parts of the city included activists of the Muttahida Qaumi Movement and the ruling Pakistan People's Party (PPP), Pakistan's Daily Times reported.
The violence comes as Muslims have been observing Ramadan, the holy month-long fasting period.
Karachi, which has a population of 18 million people belonging to various ethnic and other groups, has been hit by ethnic, political and target killings for more than four years. Various measures taken by authorities have failed to bring peace to the city, further damaging Pakistan's fragile economy and adding to its other problems related to fighting terrorism and militant violence.
Some reports say at least 300 people have died in the latest round of killing in the city which began last month.
The federal government has offered rewards for those providing information and other details of those involved in the killings. It has also given police powers to paramilitary forces deployed in the city.
The violence has largely involved supporters of the Urdu-speaking Muttahida Qaumi Movement and the Awami National Party representing mostly the ethnic Pashtuns.
Until recently the MQM, which is mostly made up of immigrants from India, has been the main force in Karachi and its politics. However, it role now is under challenge from the Pashtuns.
Authorities say local underworld dons and their supporters also have been involved in the city's violence.