‘A gunman disguised as a policeman killed at least 16 people, including a female police officer, in what is believed to be Canada's worst mass shooting.

The 12-hour rampage started on Saturday and ended with a car chase.

Police said the suspect shot people at different locations in Nova Scotia, many of them randomly. He was killed in a confrontation with police.

He was reported to have been driving what looked like a police car.

Residents had been advised to lock themselves indoors the rural town of Portapique after the attack began.

Authorities were still trying to establish the final death toll on Sunday. They warned that there may be more victims.

Royal Canadian Mounted Police Constable (RCMP) Heidi Stevenson, who had served in the force for 23 years, was among those killed.

"Heidi answered the call of duty and lost her life while protecting those she served,"

"Two children have lost their mother and a husband his wife. Parents lost their daughter and countless others lost an incredible friend and colleague," Commissioner Bergerman said.

RCMP Commissioner Brenda Lucki said she believed the gunman had an initial "motivation" at the beginning that "turned to randomness", according to CBC News.

Canadian Prime Minister Justin Trudeau described it as "a terrible situation" and Nova Scotia Premier Stephen McNeil told reporters "this is one of the most senseless acts of violence in our province's history."

Police say they were first alerted to an incident involving firearms late on Saturday.

Tweets by Nova Scotia police identified the alleged attacker as 51-year-old Gabriel Wortman.

He was not employed by the Royal Canadian Mounted Police but "may be wearing a RCMP uniform", they said. (BBC)