Two police officers were among four people killed on Friday in a shooting in eastern Canada and a suspect has been arrested, authorities said.

Authorities in the city of Fredericton urged people in the Brookside neighbourhood, where residents reported waking to the sounds of dozens of shots, to remain in their homes, describing it as an “active incident” on Twitter.

Around an hour after giving the first word of the killings, the second message from police said: “At this time, we can confirm that we have one suspect in custody.” “Police continue to have the Brookside area contained for the foreseeable future as the investigation is ongoing,” police added.

Then came word from police that “of the four people killed in this morning's shootings on Brookside Drive, two were Fredericton police officers.” The circumstances of the shooting in the capital of New Brunswick province, home to about 60,000 people, were not immediately clear.

Canadian public broadcaster CBC said that the shooting happened in a residential area of the city north of downtown, and that heavily armed police, paramedics and firefighters were on the scene.

Witnesses described to the Canadian Broadcasting Corporation seeing the barrel of a rifle or shotgun poking out from the window of a low-rise apartment and shots being fired into its courtyard.

The CBC quoted Robert DiDiodato, who lives in the area, as saying he heard a series of “firecracker” sounds around 7 am.

“With the tempo, it might've been a gunshot,” he said. “It was sort of like a pop, pop, pop, pop.” He said that about five minutes later he could hear similar sounds near his home.

“Doors are locked and everybody's inside,” he said, according to CBC.

Another resident, who gave his name only as Justin, told the broadcaster: “I woke up and I heard gunshots and I looked outside my window.

“The cops were trying to put one of the officers in their vehicle to take them out to safety,” he said.

During the fracas some residents could be seen being escorted by police out of their homes, while a nearby daycare, coffee shop and other businesses were on lockdown.

PM sends condolences

“Awful news coming out of Fredericton,” Prime Minister Justin Trudeau said in a Twitter message.

“My heart goes out to everyone affected by this morning's shooting. We're following the situation closely,” he said.

“On behalf of all New Brunswickers, I offer my condolences, thoughts and prayers to the victims and their families. During this difficult time, our thoughts are also with the courageous women and men on the front lines working to keep us safe,” said New Brunswick Premier Brian Gallant.

In 2014, three federal police officers were killed and two more were injured after responding to an emergency call about an armed man roaming a residential neighborhood of nearby Moncton, New Brunswick.

A 28-hour manhunt ensued before police caught up to the suspect and arrested him, in what was described as the second-deadliest attack on the Royal Canadian Mounted Police (RCMP) since four officers were ambushed on a Mayerthrope, Alberta farm in 2005.

More recently on July 22, a man opened fire in a bustling nightlife district of Toronto, killing an 18 year old woman and a 10 year old girl and wounding 13 other people.

The Islamic State group claimed responsibility but Canadian police said they had no evidence the group was behind the shooting.