"Our search for the suspect is still ongoing," RCMP Cpl. Chantal Farrah told a news conference Thursday afternoon. "Our focus remains in the mountain north area."
Farrah urged residents to keep their doors locked. "Stay at home, bar your doors and be vigilant," she said. "I know it's hard for families. You are in your house, you are locked, you have your kids, you want to go outside. But the police are saying to stay in."
Police were using air support, tactical teams and canine units, she said. Several hundred officers from New Brunswick and elsewhere from across Canada were involved.
"We have deployed a large amount of resources from here and elsewhere, and we are well-equipped to face this situation," Farrah said.
The 24-year-old suspect, Justin Bourque, was spotted three times around the search area Thursday morning, said Commander Marlene Snowman.
Bourque was wearing military camouflage and carrying two rifles in a picture released by police on Twitter.
At one point, he was seen coming in and out of a wooded area, Snowman said. "He's capable of moving into the wooded area and out," she said.
Investigators have not determined a motive for the shooting Wednesday evening, in which three officers were killed while responding to a call about an armed man at the north end of Moncton. Two other officers were wounded.
Police declined to identify the dead or injured officers.
It was the deadliest attack on the Royal Canadian Mounted Police since four officers were killed by a gunman on a farm in the western Canadian province of Alberta in 2005. That attack remains the deadliest on Canadian police officers in 120 years.
Snowman said Bourque was not known to police.
Schools and government offices were closed, and the city pulled its buses off the roads. Mail delivery was suspended.
Police commandeered armored trucks and told residents to stay indoors.
Commanding Officer Roger Brown said the two wounded officers underwent surgery for non-life-threatening injuries Thursday and he met with their families. One was later released from hospital.
"The RCMP family is hurting. As is Moncton, New Brunwick and our country," Brown said.
The homicides were the first this year in Moncton, a city of 69,000 people about 180 miles (290 kilometers) east of the Maine border. RCMP Constable Damien Theriault said the city had no homicides last year.
"We have been blessed until this point," Theriault told The Associated Press.
Police released a map of a large portion of the northwest section of the city, including a heavily wooded area, where they wanted people to remain indoors with their doors locked. Families hunkered down in their basements.
Daniel St. Louis, a commercial photographer, said he came upon the scene around 8:30 p.m. Wednesday and saw two blood-stained police vehicles on separate streets.
One of the vehicles, a marked police cruiser, was surrounded by shattered glass. The other, an unmarked SUV with its lights on and the driver's side door left ajar, had several bullet holes through its front windshield.
"I walked over and I saw two feet, facing the street, toes up," said St. Louis, 51. "I realized, 'Oh my God. There's somebody down.' As I got close, I realized it was an officer and this is not a good situation."
St. Louis said he didn't know what to make of the tragedy.
"Our quiet little city, what is going on here?" he said. "How is this happening to us? It always happens to somebody else."
Tim Holt said he and his daughter had been locked down in their home for hours. Holt's wife worked late Wednesday and wasn't allowed to join her family.
"I've just been locked in with my baby girl," Holt said by telephone as his 1-year-old daughter Leigha babbled in the background.
"I've got the radio and the news channel on. ... I've been going from the backyard window to the front door and back to the backyard. It's kind of ridiculous, but it's all I can do."
A few blocks away, Conrad Gagnon, 53, said he was playing a video game in his living room when he spotted a man through a window.
"It was like he was meditating on something and talking ... like somebody on drugs and living in his own world," he said. "He was talking to himself. I saw his lips moving."
Shortly afterward, Gagnon said he heard gunfire.
"I heard five or six shots, and after that another five or six shots," he said.
Such violence is rare in Canada, particularly on the east coast.
The three officers were the first Canadian police killed in the line of duty since March 2013, when a police officer in northern Quebec was shot after responding to a domestic violence call.
According to the Royal Canadian Mounted Police website, the last officer to die from a gunshot wound was on Nov. 5, 2007. Constable Douglas Scott was shot while responding to a call for help involving an impaired driver at Kimmirut, Nunavut.
In 1974, two Moncton officers were kidnapped, shot and killed after making a traffic stop.
Canadian Prime Minister Stephen Harper, in Brussels for a meeting of the G-7 group of nations, offered his condolences to the families, colleagues and friends of those affected by the shootings.
Associated Press writer Rob Gillies in Toronto contributed to this report.