Gunmen on tricycles on Friday killed nine female health workers conducting anti-polio vaccination in a twin attack.
The Police Public Relations Officer in the state, Mr Magaji Majiya, confirmed the development to the News Agency of Nigeria (NAN) in Kaduna.
Majiya said that the attack took place around 9am on Friday in Kano metropolis.
He said: "unknown gunmen riding tricycles carried out the twin attacks at Filin Cashew in Anguwa Uku and Hotoron Hayi Health Centres at the same time".
He said seven of the victims were killed at Hotoro and two others at Anguwa Uku, and the police had deposited their corpses at Murtala Mohammed Specialist Hospital.
The spokesman, however, said no arrest was made, but assured that investigation into the incident had commenced in earnest.
Meanwhile, Dr Labaran Yusuf, the state Commissioner for Health also confirmed the incident.
Yusuf said six health workers were attacked at the Anguwa Uku Health Centre,, two died on the spot and the remaining four who suffered severe injuries were hospitalised.