OSLO, Norway >> A gunman opened fire in Oslo’s nightlife district early Saturday, killing two people and leaving more than 20 wounded in what the Norwegian security service called an “Islamist terror act” during the capital’s annual LGBTQ Pride festival.

Investigators said the suspect, identified as a 42-year-old Norwegian citizen originally from Iran, was arrested after opening fire at three locations in downtown Oslo.

Police said two men, one in his 50s and and the other his 60s, died in the shootings. Ten people were treated for serious injuries, but none of them was believed to be in life-threatening condition. Eleven others had minor injuries.

The Norwegian Police Security Service raised its terror alert level from “moderate” to “extraordinary” — the highest level — after the attack, which sent panicked revelers fleeing into the streets or trying to hide from the gunman.

The service’s acting chief, Roger Berg, called the attack an “extreme Islamist terror act” and said the suspect had a “long history of violence and threats,” as well as mental health issues.

He said the agency, known by its Norwegian acronym PST, first became aware of the suspect in 2015 and later grew concerned he had become radicalized and was part of an unspecified Islamist network.

Norwegian media named the suspect as Zaniar Matapour, an Oslo resident who arrived in Norway with his family from a Kurdish part of Iran in the 1990s.

The suspect’s defense lawyer, John Christian Elden, said his client hadn’t talked to investigators, and he cautioned against speculation on the motive.

“He has not given any reason. It is too early to conclude whether this is hate crime or terrorism,” Elden said in an email to The Associated Press.

Upon the advice of police, organizers canceled a Pride parade that was set for Saturday as the highlight of a weeklong festival. Scores of people marched through the capital anyway, waving rainbow flags.

Police attorney Christian Hatlo said it was too early to say whether the gunman specifically targeted members of the LGBTQ community.

“We have to look closer at that, we don’t know yet,” he said.

Police said civilians assisted them in detaining the man in custody, who was being held on suspicion of murder, attempted murder and terrorism, based on the number of people targeted at multiple locations.

Investigators seized two weapons after the attack: a handgun and an automatic weapon, Hatlo described both as “not modern” but did not give details.

Not far from Oslo’s cathedral, crime scene tape cordoned off the bars where the shootings took place, including the London Pub, which is popular with the city’s LGBTQ community.

Crowds gathered outside and dropped off cards and flowers at impromptu memorials.

Martin Ebbestad, 29, had walked by earlier, seen the memorials and returned with flowers.

London Pub “is our go-to place. My boyfriend left 20 minutes before (it happened). He was sitting outside in the smoking area,” Ebbestad said. “We know this place so well. It doesn’t feel unsafe, but it does feel very close.”

Olav Roenneberg, a journalist from Norwegian public broadcaster NRK, said he witnessed the shooting.

“I saw a man arrive at the site with a bag. He picked up a weapon and started shooting,” Roenneberg told NRK. “First I thought it was an air gun. Then the glass of the bar next door was shattered and I understood I had to run for cover.”

Another witness, Marcus Nybakken, 46, said he saw a lot of people running and screaming and thought it was a fistfight.

“But then I heard that it was a shooting and that there was someone shooting with a submachine gun,” Nybakken told Norwegian broadcaster TV2.

Norwegian Prime Minister Jonas Gahr Stoere called the shooting a “cruel and deeply shocking attack on innocent people.”

He said that while the motive was unclear, the shooting had caused fear and grief in the LGBTQ community.

“We all stand by you,” Gahr Stoere wrote on Facebook.

Christian Bredeli, who was at the London Pub, told Norwegian newspaper VG that he hid on the fourth floor with a group of about 10 people until he was told it was safe to come out.

“Many were fearing for their lives,” he said. “On our way out we saw several injured people, so we understood that something serious had happened.”

Norwegian television channel TV2 showed footage of people running down Oslo streets in panic as shots rang out in the background.

Police said the suspect had a criminal record that included a narcotics offense and a weapons offense for carrying a knife.

PST said it spoke to him in May this year “because he had shown a certain interest in statements that were interpreted as insults to Islam.”

“In these conversations, it was assessed that he had no intention of violence, but PST is aware that he has had challenges related to mental health,” the agency said in a statement.

Police advised organizers of the Pride festival to cancel a parade scheduled for Saturday.

“Oslo Pride therefore urges everyone who planned to participate or watch the parade to not show up. All events in connection with Oslo Pride are canceled,” organizers said on the official Facebook page of the event.

Inge Alexander Gjestvang, leader of FRI, a Norwegian organization for sexual and gender diversity, said the shooting shook the Nordic country’s LGBTQ community.

“We’ll be back later, proud, visible, but right now it’s not the time for that,” he told TV2.

Norway’s King Harald V offered condolences to the relatives of victims and said the royal family was “horrified” by the attack.

“We must stand together to defend our values: freedom, diversity and respect for each other. We must continue to stand up for all people to feel safe,” the monarch said.

World leaders condemned the attack on their way to a Group of Seven summit in Germany. The summit’s host, German Chancellor Olaf Scholz, tweeted, “The Norwegian people can be sure of our sympathy. The fight against terror unites us.” French President Emmanuel Macron offered his condolences in a tweet in Norwegian.

John Kirby, spokesman for the White House National Security Council, told reporters while flying with U.S. President Joe Biden to the G-7 summit, “Our hearts obviously go out to all the families there of the victims, the people of Norway, which is a tremendous ally, and of course the LGBTQI+ community, there and around the world, quite frankly.”

Norway has a relatively low crime rate but has experienced a series of so-called lone wolf attacks in recent decades, including one of the worst mass shootings in Europe. In 2011, a right-wing extremist killed 69 people on the island of Utoya after setting off a bomb in Oslo that left eight dead.

In 2019, another right-wing extremist killed his stepsister and then opened fire in a mosque but was overpowered before anyone there was injured.

Last year, a Norwegian man armed with knives and a bow and arrow killed five people in a town in southern Norway. The attacker, who was diagnosed with schizophrenia, was sentenced Friday to compulsory psychiatric care.