A gunman opened fire in the historic heart of Kraków on Saturday, killing six people and wounding at least 15 others, in one of the worst mass shootings in Poland's modern history. Police later found the bodies of three of the suspect's close family members at his home.

The attack began shortly after 3 pm local time in the Main Market Square, the vast medieval plaza at the centre of Kraków's UNESCO-listed Old Town and one of Poland's most visited tourist sites. Police said the gunman drove into the square and fired at random from his car, stopping at several points to shoot at people in the crowded plaza.

What police have confirmed

Six people were killed — four women and two men. At least three of the women were Polish, and one of the dead was a British citizen, authorities said. Sixteen people were hurt in total, including the gunman himself, who was shot and wounded by police before being taken into custody and to hospital. Five foreign nationals were among the injured, from Austria, Germany, Portugal, Russia and Britain, and two police officers were wounded.

Police identified the suspect as a 24-year-old Polish citizen and said he acted alone, adding that there was no continuing threat to the public. He was wearing military-style clothing, a helmet and a bulletproof vest, and used an AR-15 rifle, according to police. The weapon was held on a firearms licence.

Hours after the attack, Prime Minister Donald Tusk said the bodies of two women and a man had been found at the suspect's home in Ostrowiec Świętokrzyski, about 200 kilometres north of Kraków. Several Polish outlets reported that the three were the gunman's parents and sister, killed earlier in the day.

Far-right views, say ministers

Interior Minister Marcin Kierwiński told a news briefing that the attacker held radical, ultra-nationalistic views and was fascinated by far-right ideologies. "Everything points to the fact that the shooter was influenced by far-right ideology, a matter that will also be subject to investigation," he said. Investigators have not yet established a definitive motive.

Defence Minister Władysław Kosiniak-Kamysz described the attack as an "act of terror" and denied reports that the suspect was a soldier. President Karol Nawrocki will declare a period of national mourning on November 8 and 9, his office said, while Kraków's mayor declared mourning in the city until November 11.

Mr. Tusk praised the two officers who confronted the gunman, Senior Constables Jakub Kulik and Artur Morański, calling them "true heroes". Video of the confrontation showed an officer firing at the gunman as he stood beside his car.

The shooting has shocked a country that has long viewed itself as safer than western European neighbours that have suffered such attacks. It also follows a string of school stabbings in October that authorities said were influenced by violent and extremist content online — a connection investigators will now examine closely.