The bodies were found during a search of the suspect's residence in Ostrowiec Świętokrzyski.

"There are probably dead people in the attacker's house. We will confirm this. This is what the drone image shows," Polish Prime Minister Donald Tusk was quoted as saying by TVP World.

The three victims, two women and a man, are most likely the suspect's immediate family members, Tusk said, adding that further information about the deceased would be shared later.

At least six people were killed and 15 others injured after a gunman opened fire in a crowded market square in Krakow, Poland's second-largest city, on Saturday, according to authorities.

The attacker reportedly targeted people at random while driving into the city's Main Market Square, a major tourist attraction in the historic city centre.

Several police officers were also among those injured in the incident.

Police identified the gunman as a Polish national, according to local media outlet Onet. He was reportedly not carrying any identification documents when officers established his identity through an investigation.

"The man had no identification documents with him. The police were able to establish his identity through operational work," Onet quoted a police officer as saying.

Gunman shot in exchange of fire

The suspect was shot and injured during an exchange of fire with police officers a short distance from the site of the initial attack.

Katarzyna Cisło, a spokesperson for Krakow Police, told local broadcaster TVN24 that the attacker was wearing military-style fatigues and carrying a military-type long gun.

Cisło said the man had acted alone and that there was no longer any danger to the public.