Four women and two men have been killed in a shooting in Krakow, police say, with about a dozen more injured.
Two police officers are among the injured - one is in a "critical condition", Interior Minister Marcin Kierwiński said.
Police said the suspect - a Polish citizen - was shot by officers and taken to hospital.
Meanwhile, a police spokesperson said the suspect was "wearing military-style attire" and "used military weapons"
In a social media post, Polish PM Donald Tusk called the incident "tragic" and said he was being kept updated.
Tusk praised the "heroic police officers who risked their lives" to stop the shooter.
The interior minister earlier confirmed two officers were shot - one remains "in very critical condition".
Tusk appealed to colleagues "of all stripes: do not exploit this tragedy".
"We will establish all the circumstances of this crime," he added.
Graphic footage filmed at the northern corner of the square shows at least four people lying on the ground, some receiving first aid from panicked bystanders, others lying motionless.
Gunshots can be heard for more than a minute as more people are seen running away.
A clip filmed on Grodzka, a road leading south from the square, shows a black car being pursued by police at high speed. An outbreak of gunfire causes the person filming to take shelter in a cafe.
Another video filmed further along the road shows the pursuit continuing as more gunshots are fired.
The shooting seems to have ended near a large intersection just over 1km south of the square.
Footage taken at the scene shows a police officer firing multiple times at very close range at a person who appears to be dressed in military-style fatigues lying on the ground. The officer then slumps to the ground, apparently injured.
Footage filmed at the same location a short while afterwards shows two men, one in police uniform, one in military clothing, receiving treatment. A rifle can be seen lying on the street near the two men.
