LONDON -- Norwegian Police Security Service raised its terror alert to the highest level after a shooting in the country's capital left two people dead and several others injured, according to The Associated Press.
Two people were fatally shot and 10 were injured early Saturday in a nightclub in Oslo, Norway, in what Oslo police now suspect was a terror attack.
Authorities say the gunman, identified as a 42-year-old Norwegian citizen originally from Iran, was arrested after opening fire at three locations in downtown Oslo at approximately 1 a.m., including at a nightclub that is popular within the LGBTQ community called The London Pub.
Police attorney Christian Hatlo confirmed that the unnamed suspect was being held on charges of suspicion of murder, attempted murder and terrorism, and that the suspect's mental health was also being investigated.
"Our overall assessment is that there are grounds to believe that he wanted to cause grave fear in the population," Hatlo said. "We need to go through his medical history, if he has any. It's not something that we're aware of now."
Acting Norwegian police chief Roger Berg called the shootings an "extreme Islamist terror act." He said the gunman had a "long history of violence and threats," according to the AP.
According to The Associated Press, Hatlo said the suspect was known to Norwegian authorities but had no history of violent crimes. Hatlo confirmed that the suspect's criminal record included a narcotics offense as well as a weapons offense for carrying a knife.
Authorities said they were able to seize two weapons following the suspected terror attack, including a handgun and an automatic weapon which Hatlo described as "not modern" but gave no further details.
Two of the shooting victims were killed, Oslo police inspector Tore Soldal said. He also confirmed that the other 10 victims were being treated for serious injuries but that all 10 were expected to survive.
"I saw a man arrive at the site with a bag. He picked up a weapon and started shooting," said Olav Roenneberg, a journalist from Norwegian public broadcaster NRK who said he witnessed the attack. "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."
White House spokesman John Kirby expressed condolences for victims of the attack and said the U.S. stands in solidarity with Norway, its close ally.
"we're all horrified by the mass shooting in Oslo today targeting the LGBTQI+ community there and our hearts obviously go out to all the families of the victims, the people of Norway, which is a tremendous ally, of course, the LGBTQI + community there and around the world," Kirby said. "I do want to add that we've been in touch with the Norwegian government to offer our condolences and also to offer any support that they might need as they continue to investigate this."
Following the shooting, Oslo Pride confirmed that it has been advised by authorities to cancel the annual Pride parade and other Pride events that had been scheduled for this weekend.
"Oslo Pride therefore urges everyone who planned to participate or watch the parade to not show up. All events in connection with Oslo Prides are canceled," Oslo Pride organizers said on the official Facebook page of the event.
"The shooting outside London Pub in Oslo tonight was a cruel and deeply shocking attack on innocent people," said Norway's Prime Minister Jonas Gahr Stoer in a Facebook post following the attack.
Store added that the mass shooting had caused immediate fear and grief within Norway's LGBTQ community.
"We all stand by you," Store wrote.
ABC News' Rashid Haddou, Lama Hasan, Ahmad Hemingway and Will Gretsky contributed to this report.