A 19-year-old student was arrested after four young children and two adults were found dead at a suburban home near Canada's capital city Ottawa, police said Thursday.

Police said they rushed to a home in the Ottawa suburb of Barrhaven after receiving a call at 11:00 pm Wednesday evening (0400 GMT Thursday).

At the scene, police discovered the bodies of four children, their 35-year-old mother and a 40-year-old man, whom police described as a family "acquaintance" also living there.

The children were a newborn aged two-and-a-half months old, as well as a two-, four- and seven-year-old.

Their father, the woman's husband, was found injured and taken to hospital, where police said he was in critical condition.

Authorities said that an "edged weapon" had been used to kill and injury the family members, who were described by Police Chief Eric Stubbs as "newcomers to Canada... originally from Sri Lanka."

The suspect arrested Wednesday evening, also of Sri Lankan origin, was "an acquaintance of the family and was living in the house at the time," Stubbs said at a press conference Thursday afternoon, without providing any further details of the links between them.

"This was a senseless act of violence perpetrated on purely innocent people," he said, describing the "mass killing" as extremely rare or even unprecedented for Ottawa.

Canada's Prime Minister Justin Trudeau expressed his "shock and horror" at what he called a "terrible tragedy."

Speaking at a press conference, Trudeau said: "Obviously, our first reactions are all ones of shock and horror at this terrible violence... And we expect the police of jurisdiction to be doing the work and keeping us all informed of this terrible tragedy."

Ottawa's mayor Mark Sutcliffe wrote on X, formerly Twitter: "I was devastated to learn of the multiple homicides in Barrhaven, one of the most shocking incidents of violence in our city's history.

"We are proud to live in a safe community but this news is distressing to all Ottawa residents."