A gunman who drove a mock-up police car killed at least 18 people in an Atlantic Canada shooting rampage, federal police said on Sunday, the worst case of its kind in Canadian history.

The shooter, identified as Gabriel Wortman, 51, was shot dead by officers after a 12-hour manhunt in Nova Scotia province ended on Sunday morning.

Among the victims was a veteran female constable with the Royal Canadian Mounted Police, which also handles municipal and provincial law enforcement in the province.

Police said the suspect had been on the run since Saturday night, when officers were alerted to shots fired in the town of Portapique, around 100 kilometres (60 miles) from Halifax.

Gun violence in Canada is far less frequent than in the neighbouring United States, and weapons more strictly controlled, but the killings were the country's worst ever, exceeding the toll in 1989 when a gunman murdered 14 female students at Montreal's Ecole Polytechnique.

Public broadcaster CBC quoted RCMP Commissioner Brenda Lucki as saying police know of at least 16 victims, besides the shooter.

"What has unfolded overnight and into this morning is incomprehensible and many families are experiencing the loss of a loved one," Nova Scotia RCMP Commanding Officer, Assistant Commissioner Lee Bergerman, wrote on the force's local Facebook page.

"That includes our own RCMP family. It is with tremendous sadness that I share with you that we lost Constable Heidi Stevenson, a 23-year veteran of the Force who was killed this morning, while responding to an active shooter incident."

In addition to Stevenson, a mother of two, a male officer was injured and is in hospital with non-life threatening injuries, Bergerman said.

The National Post newspaper said another victim was an elementary school teacher, citing a Facebook post from the woman's sister.

Several victims were discovered both outside and inside a house in Portapique, sparking the manhunt through multiple communities, police said.

"The search for the suspect ended this morning when the suspect was located. And I can confirm that he is deceased," RCMP Chief Superintendent Chris Leather told a press conference.

Leather said that at one point, the suspect appeared to be wearing part of a police uniform and was driving a vehicle made to look like an RCMP cruiser.

Fires burned

RCMP tweeted several times that he was not an officer and warned he was considered "armed and dangerous."

"The initial search for the suspect led to multiple sites in the area, including structures that were on fire," Leather told the news conference.

Another police spokesperson said, without further details, that the gunman was killed after an officer intervened.

An independent agency, the Serious Incident Response Team (SiRT), which probes certain incidents involving the province's police, said that it "is investigating the shooting of a male in Enfield by RCMP officers."

SiRT said in a statement that a confrontation had occurred in Enfield, which is near the Halifax airport, "resulting in officers discharging their firearms. The suspect was found to be deceased at the scene."

Police said they had no indication of a motive. Lucki told CBC there was no indication "at this point" of a terrorist intent.

"What I would say is that it appears to be at least in part, very random in nature," said Leather.

"We are in the early stages of an incredibly detailed and complex investigation that has forever changed countless lives," he said.

Prime Minister Justin Trudeau said in a statement that he "was saddened to learn about the senseless violence in Nova Scotia," and he hopes for a full recovery of the wounded.

The National Post quoted Tom Taggart, a councillor who represents Portapique in the Municipality of Colchester, as saying the community was devastated.

He described the community as a "subdivision in the woods where people have acre lots along the shore," and where Wortman owned three properties.

"It's absolutely unbelievable this could happen in our community. I never dreamt this would happen here," Taggart said.

Death toll rises to 18

On Monday, Canadian Prime Minister Justin Trudeau said that the death toll from the shooting rampage had risen to at least 18.

“Our country stands united in our effort to defeat a pandemic, to save lives and to help each other make it to a better day,” he told a news conference.

“But yesterday we were jolted from that common cause by the senseless violence and tragedy in Nova Scotia, where a gunman claimed the lives of at least 18 people.”

“No one man's action can build a wall between us and a better day — no matter how evil, how thoughtless, or how destructive,” Trudeau added.