At least six people including a British citizen have been killed and more than 15 people have been wounded in a “terror attack” in Kraków, according to Polish authorities.

Commander-in-chief of  Poland’s police, Marek Boron, said three victims were Polish and one was British. Two are still to be identified.

Two women and a man were also found dead at the perpetrators house, Polish Prime Minister Donald Tusk confirmed on Saturday night, adding that they are likely members of the attacker’s family.

The fatal incident took place in the Main Market square of Kraków at roughly 3pm local time (2pm GMT), and emergency services remain at the scene.

Kraków Mayor Łukasz Gibała signed an order declaring a period of mourning in the city lasting until Wednesday, November 11.

Police said that the alleged gunman was a 25-year-old Polish citizen. “The only known perpetrator of the incident is in police custody,” they said in a post on X.

“A man who had driven onto the square began firing at random people from his car,” Polish police also revealed in a statement. “The perpetrator has been detained. Several people have been injured, including police officers.”

The man, who was shot by officers, used a long military-type firearm and was in military-style dress, they said.

Police spokesperson Andrzej Fijolek told broadcaster TVN 24 the attacker used an AR-15 rifle and that had a firearms licence.

Interior Minister Marcin Kierwiński said there is no reason to believe there was more than one attacker but added that he had “very radical views”.

Everything indicates he was inspired by “far-right ideologies”, he said.

Polish Defence Minister Wladyslaw Kosiniak-Kamysz described the incident as a “terror attack” and denied that the attacker is in the military.

The regional Malopolski government confirmed the death toll is six and that 16 were injured. All 16 are receiving medical care at hospitals in Kraków.

One of the two injured police officers is “in [a] very critical condition” and has undergone surgery, according to Interior Minister Kierwiński.

“Police officers in Kraków risked their lives to intervene. Immediately. Thanks to their heroic actions, the attacker was quickly apprehended,” he wrote in a statement on X. He is said to be heading to the scene of the shooting.”

Officers shot at the attacker just three minutes after receiving a call about the incident.

An eye witness told Reuters that she saw a man inside a car who started shooting before she ran to hide in a restaurant.

A post from the official Kraków X account said: “A crisis response team is operating at City Hall. Emergency services are still working at the scene. I ask everyone to remain calm and act responsibly. Our thoughts are with the victims’ loved ones.”

In a post on X, Polish prime minister Donald Tusk said: “My highest praise for the heroic police officers who risked their lives. And a heartfelt appeal to politicians of all stripes: do not exploit this tragedy. We will establish all the circumstances of this crime.”

People have been urged to stay away from area and to call emergency services if they are in danger.

Prime Minister Andy Burnham expressed Britain’s support for Poland, writing on X: “I’m shocked and saddened by the appalling shooting in Kraków today.

“My thoughts are with the families of those who have lost their lives, everyone injured and all those affected by this senseless violence.

“The United Kingdom stands in solidarity with the people of Poland.”

The shooting took place in Kraków’s main square Rynek Glowny – an area usually teeming with people visiting the bars and restaurants on a Saturday afternoon and home to a popular Christmas market.

The square has been cornered off and reports from the scene describe a heavy presence of police, fire trucks and ambulances.

Poland’s president, Karol Nawrocki, said on social media that he is “deeply concerned” by the tragic event and expects “a full explanation of the circumstances” surrounding the shooting.

He added that the head of the national security bureau is on his way to Kraków.

Justice minister Waldemar Żurek has appealed for calm and said the perpetrator will be “severely punished” in a statement on X: “I share the grief of the families and loved ones of the victims of this unimaginable tragedy…

“We appeal for calm and ask that people not interfere with the work of the emergency services. We will ensure that the perpetrator of this crime is held fully accountable and severely punished.”

Tom Rose, the US ambassador to Poland, was among the first international officials to share his support for the country in the wake of the shooting.

He said in a post on X that the “savage and murderous attack” has shattered the peace of Poland.

He added: “America stands with Poland at this dark hour as Poland stands with her beloved citizens of Kraków. May the blessed memory of those lost today assuage the grief of those who mourn.”

Wrocław, a city north of Krakow, has also brought in tighter security measures. “It is hard to believe what happened today in Krakow,” Wrocław mayor Jacek Sutryk says in a statement. “A huge tragedy and unimaginable pain for the families who lost their loved ones.”