An ambulance helicopter at Krakow's main market square. ( Agencja Wyborcza: Jakub Włodek via Reuters )
Four women and two men have been killed and 15 others injured in a shooting in Krakow's main market square, according to local authorities.
Malopolska Police said officers had shot at the "perpetrator", who was taken hospital.
Katarzyna Cisło, a spokesperson for the Krakow police, said the shooter, a 24-year-old Polish citizen, was wearing military-style fatigues and a bulletproof vest and used a military-type long gun in the attack.
Police found many other weapons, as well as ammunition, in his car.
He kept firing at the police even after being shot himself, she said.
Ms Cisło added that the gunman acted alone and that the public was now safe.
The gunman was aiming at random people as he drove into the Main Square, a major tourist destination in the centre of the city, Krakow police said.
The motive behind the attack remains unknown.
About 15 million tourists a year visit Krakow — Poland's second largest city. The majority passes through the Main Square.
Chairs and pillows lie on the ground after a shooting. ( Reuters: Jakub Porzycki )
Polish Interior Minister Marcin Kierwiński said one of the police officers injured in the shooting was in a "critical condition".
In a post on X, he said the officer had suffered "three gunshot wounds" and was undergoing surgery.
Polish Prime Minister Donald Tusk is travelling to Krakow.
He described the shooting as "tragic" and said he was "being kept informed" about the situation.
"A heartfelt appeal to politicians of all stripes: do not exploit this tragedy," he wrote on X.
Police secured the area, where authorities are investigating the incident. ( Agencja Wyborcza.pl: Jakub Włodek via Reuters )
Images from the scene showed police officers and ambulances covering the area, and a Polish Medical Air Rescue helicopter also landed in the square.
Krakow's public transport provider MPK said one of its trams was also shot at from a car just after 3pm local time.
In a post on X, it said the window of the driver's cab had been shattered, but no-one on the tram had been injured.
President Karol Nawrocki said he was "deeply concerned".
Krakow's Mayor Lukasz Gibala asked for "calm and responsibility".
"Our thoughts are with the victims' loved ones," he wrote on X.
The US ambassador to Poland has also shared his concern.
"We are just learning details of the horrific mass shooting in Krakow, a savage and murderous attack that's shattered the peace of Poland," Tom Rose wrote on X.
"America stands with Poland at this dark hour as Poland stands with her beloved citizens of Krakow."
The European Commission's vice-president Kaja Kallas said the shooting was a 'tragedy", adding that, "Poland does not stand alone".
"The tragic loss of life in the shooting in Krakow is a tragedy that will be felt far beyond Poland," the EU's top diplomat said on X.
"My thoughts are with the victims and their families and the first responders."
