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Oslo, Norway (CNN) -- The scene after a bomb exploded in the center of Oslo on Friday reminded New Yorker Ian Dutton of what he witnessed after the September 11, 2001, terrorist attacks in the United States.
The scale of the Oslo explosion was smaller than that of 9/11, but the stunned feeling and confusion in the aftermath were eerily similar.
"Seeing the emergency response gives me that same feeling in my spine of being in someone's crosshairs," Dutton said.
The roads near the government buildings that were the target of the attack were free of most people except emergency responders, whose reflective yellow jackets contrasted with their surroundings.
Debris covered the streets -- pieces of metal, poles and glass littered the area.
Photos from the state-run broadcaster NRK showed emergency personnel putting people on stretchers and wheeling them through the debris from the blast.
Video showed one government building with its windows mostly blasted out along one side.
The blast could be felt for miles, witnesses said.
"It rocked me out of bed," Dutton said.
"The building that sustained the explosion had a helipad on its roof and now has beams hanging from it," Dutton said. Most of the windows were blown out, and curtains were dangling. "I can see the warped metal of the building," he said.
There was a line of yellow ambulances by the scene, and a police cordon kept onlookers back.
"I didn't know Oslo had so many ambulances," he said.
"Everything is like a movie," said Paul Ronneberg, who works three blocks from the explosion. "You can feel some kind of mystic energy surrounding the town. It's very quiet. Most of the city center is closed of the police. The smiling Norwegian people aren't smiling anymore."
Emily Anderson, a 22-year-old waitress from Fargo, North Dakota, was in Norway on her second day of a family vacation.
"I was in a store with a younger sister and a younger cousin and we were in there shopping and heard a humongous bang and felt an explosion," she said. "We were on a lower level of a store and when we heard it, we gathered at the front doorway of the store. You could see tons of smoke pouring out of this building. It was extremely loud."
Others on the street appeared to be in shock, she said. "I thought we were going to die. It was scary. It felt like 9/11."
"It sounded like a thunderclap, but louder than a thunderclap could be," said Anderson's 33-year-old cousin, Dawn Lubka, a nurse from Minneapolis who was in her room at the Comfort Hotel Borsparken in Oslo when the blast occurred. She said she initially assumed it was a construction accident, as there are lots of new buildings and a new opera center going up nearby.
But when she looked online, she found out what had really happened. "I asked the concierge, politically, why would they have bombings here? The Norwegians couldn't believe that it could be a bombing in their city. He said, honestly, 'It's because we're friends with you. Because (Norway) is helping with troops in Afghanistan.'"
Morten Vaage said he was about 800 meters from the explosion when it occurred after he had attended a parade to welcome his brother and other soldiers back from Afghanistan.
At the parade, the Norwegian defense minister, Grete Faremo, had addressed the soldiers "and emphasized how lucky we are to live in this country of Norway, where we are safe and free," he said.
The explosion soon after contrasted sharply with her words. "It did not feel like Norway," he said. "I heard the explosion and the whole central (train) station shook. ... People were shocked; some were crying, some were bleeding."
Ulrik Fredrik Thyve was finishing a day's work when he heard the "huge, enormous bang."
"The explosion was immense; my office felt like it contracted, expanded, and windows were blown all over the building," he said. "Dust, smoke, people bleeding everywhere. I walked out and towards ground zero to see if there was anything to do."
Police evacuated him and his co-workers from the area.
Nick Soubiea, an American-Swedish tourist in Oslo, said he was less than 100 yards from the blast, which he described as deafening.
"It was almost in slow motion, like a big wave that almost knocked us off our chairs," he told CNN. "It was extremely frightening."
He said the streets were crowded with people trying to get away from the center of the city. "There are people running down the streets, people crying, everyone's on their cell phones calling home," he said.
CNN's Mariano Castillo, Nicole Saidi, Carly Costello, Jesicca Ellis, Joe Sterling and Moni Basu contributed to this report.