At least six people were killed and 15 wounded when a gunman opened fire from a car on the Main Market Square in Krakow, southern Poland, on Saturday afternoon, in an attack the Polish prime minister has called an act of terrorism.

Police said a man drove onto the square at about 3pm local time (14:00 GMT) and “began firing at random people from his car”, according to Al Jazeera. Four women and two men were killed. Officers shot and detained the gunman, who acted alone, and he was taken to hospital for treatment.

Polish police chief Marek Boron said a British national was among the dead and five foreign nationals were among the wounded in hospital. Two of the victims had not been identified. A police spokesperson said the man returned fire during the arrest, leaving two officers among the injured; Interior Minister Marcin Kierwinski said one officer was in a critical condition.

Kierwinski said the suspect, a Polish citizen, appeared “fascinated by far-right ideologies” and held “ultra-nationalist views”. Police said he wore military-style clothing and used a semi-automatic rifle similar to a US AR-15, with further weapons found in his car. CNN reported he is 25 years old.

Prime Minister Donald Tusk announced two days of national mourning and said three further bodies — two women and a man — were found during a search of the suspect’s home in Ostrowiec Swietokrzyski, about 190km north of Krakow. He told a crisis meeting there were “strong indications” they were members of the suspect’s immediate family.

“Until now in Poland, we haven’t had such drastic cases of terrorism,” Tusk said. “That’s what we have to call this cruel attack on people’s lives here in Krakow.”

President Karol Nawrocki said he was awaiting “a full explanation of the circumstances”, adding that the safety of Poles was “an absolute priority”.

Note on the casualty figures

The toll rose during Saturday evening. Hiru News, filing earlier and crediting CNN, reported five dead and more than 12 injured. The figures above are the later counts given by Polish police and reported by Al Jazeera and CNN, and do not include the three bodies found at the suspect’s home.