The injured included two police officers and the gunman. Thirteen were assigned the highest emergency treatment priority upon hospital admission, while one police officer was in extremely serious condition, Kierwinski said, Xinhua reported.
Four of the victims killed were identified as three Polish women and a British citizen, while the identities of the other two were still being verified. Five foreign nationals were among the injured, he added.
The gunman, a Polish national, was wearing military clothing and carrying a military-style long gun when police wounded and detained him at the intersection of Dietla and Stradom streets, a regional police representative told broadcaster TVN24. A large quantity of additional firearms and ammunition was seized from his car.
Citing unofficial police information, news website Onet reported that the suspect, 24, had fired at people randomly while driving, prompting officers to pursue him and exchange gunfire with him.
Regional police spokesperson Katarzyna Cislo said there was no confirmed evidence of a second perpetrator. The suspect had no identification documents on him, and police established his identity through operational work, she added.
Speaking in Krakow on Saturday evening, Prime Minister Donald Tusk described the shooting as a terrorist attack, saying Poland had never before experienced an act of terrorism of such severity, according to Onet.
Tusk said police, intelligence services and prosecutors would work to establish the suspect's motives as quickly as possible and make their findings public.
He also revealed that police had found three bodies -- two women and a man -- at the suspect's home in the Ostrowiec Swietokrzyski area in south-central Poland, PAP reported.
National police spokesperson Andrzej Fijolek said the victims were likely the suspect's parents and sister, although this had yet to be confirmed.
President Karol Nawrocki has declared Sunday and Monday days of national mourning, according to broadcaster RMF. Tusk said his office would coordinate the arrangements.
Krakow's municipal authorities separately announced that the city would observe the mourning days with events organized by the city government and municipal institutions canceled during the period.
Krakow Mayor Lukasz Gibala said a crisis management team was operating at city hall, urging the public to remain calm and expressing sympathy for the victims' families.
Prosecutors, police and other services were securing evidence and investigating the attack, Justice Minister Waldemar Zurek said, urging the public not to obstruct their work and pledging to hold the perpetrator accountable.
Deputy Prime Minister and Defense Minister Wladyslaw Kosiniak-Kamysz also pledged a thorough investigation into the circumstances of and motives behind the incident.