Two police officers are among four people killed in a shooting in the eastern Canadian city of Fredericton as calls mount for tighter gun controls after a spate of shootings in cities across the country in recent months.

Fredericton Police said Constables Lawrence Costello, 45, and Sara Mae Helen Burns, 43, were killed at an apartment complex after gunshots were heard about 7am on Friday.

Nearby streets went into lockdown in the normally quiet provincial capital of 56,000 as fears a second gunman was on the loose. Police issued a statement just before 12pm that there was no further threat to the public and one man was in custody with serious injuries.

They did not release the names of the two civilians who were killed, and said only that the suspect was a 48-year-old Fredericton man.

By 8pm local time, police issued a further statement: “We know people have a lot of questions, and we ask for your patience as we try to answer them, and maintain the integrity of the ongoing investigation”.

They did not release information about a possible motive or the weapon.

A local health official said that multiple shooting victims were being treated at one hospital.

Throughout the day, police and emergency services, friends and colleagues across Canada and the US sent messages of support and love to the two officers killed “in the line of duty”.

A friend of Constable Costello (who had served in the police force for 20 years), Shaun Rouse, said his long-time school friend “died a hero”.

Our deepest condolences to the families of our fallen members 45-year-old Lawrence Robert Costello and 43-year-old Sara Mae Helen Burns and the other victims in this morning's shootings. pic.twitter.com/9TeWn5OqWx

— Fredericton Police (@CityFredPolice) August 10, 2018

https://twitter.com/shawnrouse/status/1028002973828440065

David MacCoubrey, who lives in Fredericton, said he heard about 20 shots and hid on his kitchen floor.

He awoke in his apartment on Brookside Drive to the sound of three gunshots about 10 metres from his bed.

Mr MacCoubrey said his apartment complex had four buildings in a square, and it sounded like the shots were coming from the middle of the complex.

He said police have been searching the complex, including his apartment.

Earlier, local media images showed emergency vehicles converging on a tree-lined residential street.

Police were also asking people on Facebook not to use social media to report on police locations.

“It was scary,” said Marlene Weaver, who was in bed on Friday morning when she heard shots ring out in her neighbourhood. “It takes you back to the shooting in Moncton.”

She was referring to an incident in 2014, when three Royal Canadian Mounted Police (RCMP) officers were killed and two wounded in Moncton, New Brunswick, about 195 km from Fredericton, in one of the worst incidents of its kind in Canada.

The latest incident occurred just three weeks after a gunman killed two people and wounding 13 others on a street in Toronto before taking his own life.

“Awful news coming out of Fredericton,” Canadian Prime Minister Justin Trudeau said on Twitter. “My heart goes out to everyone affected by this morning’s shooting. We’re following the situation closely.”

Fredericton Mayor Mike O’Brien said the coming days would be difficult for the tight-knit community.

“The next few days will be a challenging time for our community as we deal with a loss that will no doubt be felt by many,” Mr O’Brien said in a statement.

In a tweet, he added: “Our hearts are broken by the murder of our two brave police officers. In this time of shock and grief, let us all protect their families.”

Awful news coming out of Fredericton. My heart goes out to everyone affected by this morning’s shooting. We’re following the situation closely.

— Justin Trudeau (@JustinTrudeau) August 10, 2018

https://twitter.com/mikeobrien_fton/status/1027926212771864577

At a press conference, Canada’s Public Safety Minister Ralph Goodale said the investigation was in its early stages and little was known about the shooter’s motivation.

“What we do know is that four Canadians are dead, and that is a huge tragedy for the whole country,” he said.

DEVELOPING: Police say at least four people are dead in an ongoing situation in the Canadian town of Fredericton https://t.co/5W8cRkMGee pic.twitter.com/GwUB5EnYQx

— CBS News (@CBSNews) August 10, 2018

Gun laws in Canada are stricter than in the United States but a proliferation of weapons has led to an increase in gun crimes in recent years.

In the wake of the Toronto bloodshed last month, the city council voted overwhelmingly to urge the federal government, which has jurisdiction over gun laws, to ban the sale of handguns in the city.

“Why does anyone in this city need to have a gun at all?” Toronto Mayor John Tory said.

Canada’s largest city has had 241 shooting incidents this year, resulting in 30 deaths, a 30 per cent increase in fatalities.

Bill Blair, the government minister tasked with tackling gun violence, said officials are considering giving provinces the power to designate gun-free cities.

In 2016 Canada had 0.61 firearm-related homicides per 100,000 people, a 23 per cent increase from 2015 and the highest rate since 2005, according to Statistics Canada.

For the United States, the University of Washington’s Institute for Health Metrics and Evaluation reported 3.85 deaths per 100,000 that year.

Canada’s Liberal government unveiled proposals in March to tighten already tough gun control laws to address a spike in crimes involving firearms, including a deadly attack on a mosque last year.

-with AAP