Krakow's Main Market Square remained sealed off Sunday while some mourners brought candles to pay tribute to six people killed by a gunman who authorities said was "fascinated by far-right ideologies".

A British national was among the dead, according to police. And among the 15 wounded were nationals from Austria, Britain, Germany, Portugal and Russia, authorities told the PAP news agency.

Three more bodies were later found at the suspect's home in Ostrowiec Swietokrzyski, around 150 kilomeres (95 miles) northeast of Krakow. Police said they were his parents and a sister.

The gunman was wounded by police during the rampage and is in critical condition in hospital.

The 24-year-old Polish national opened fire at random in the heart of Krakow's historic centre. Prime Minister Donald Tusk labelled the shooting as an act of "terrorism" but police did not give a possible motive.

Two police officers were wounded as they desperately chased the suspect, who was masked and dressed in military garb, including a bullet proof vest.

The man left his car at one intersection and started shooting at the two police with a semi-automatic rifle, according to police.

One police officer was in serious but stable condition, the interior ministry said, as quoted by PAP. Police appealed for blood donors for the officer, named as "Jakub Kulik, who without hesitation confronted an armed attacker".

Social media images showed the two police firing at the gunman, with one managing to wound him despite his own injuries.

On Sunday morning, the usually busy site of the attack was sealed off with red-and-white tape. People laid candles and police checked the bags of workers of the cafes and restaurants on the square.

Black flags and Poland's flags with black ribbons were seen in the city's as Warsaw announced two-day country-wide mourning for the victims from Sunday.

The suspect -- named in the media as Michal O. -- was wearing military-style clothing at the time of the attack and police also found weapons in his car, Interior Minister Marcin Kierwinski said on Saturday.

The three bodies found at the gunman's home were his parents and a sister, regional police said on social media.

The victims were a 53-year-old man and two women aged 52 and 21.

"Injuries were found on the bodies, which were preliminarily assessed as gunshot wounds... Seven firearms were seized from the flat," police added.

They said that "operations involving police counter-terrorism officers, forensic experts and a prosecutor continued at the scene throughout the night."

According to investigators quoted in the Polish media, Michal O. had no previous criminal record.

He was a member of a shooting club, along with his father.

Britain's Prime Minister Andy Burnham said he was "shocked and saddened by the appalling shooting".

@AFP