MONTREAL (AFP) - A Canadian who murdered eight people, including his wife, spared two infants during his deadly rampage, the police said, while reports emerged on Saturday that he had previously threatened his family.

The police are still investigating the motive behind the killing spree last week in Edmonton by 53-year-old Phu Lam, a man of Vietnamese origin.

But the new details shed some light into what may have prompted the killings that shocked the northern capital of the oil-rich province of Alberta at the end of December.

Last Sunday, Lam killed his wife Tien Truong, 35, her eight-year-old son, her parents, her sister, her three-year-old niece and an acquaintance of Truong's.

At a different location the next day, Lam killed a 37-year-old woman who the police say was a friend of the family and likely was not Lam's intended target.

Lam, who was believed to be depressed, later took his own life at a Vietnamese restaurant where he worked.

During a press conference on Friday, the police said there were two young children that Lam spared during his spree, leaving them at a relative's house before killing again.

The children were aged one and the other was eight months old. They may have been related to Lam, local media reported.

"There's a very good possibility that those two young children were in the house, in the north end, when the homicides took place," Deputy Police Chief Mark Neufeld said.

"For whatever reason, the two children were spared."

Two years ago, Lam had threatened to kill his family, according to a legal complaint filed by his wife.

Ms Truong accused Lam of repeated violence over the years, according to court documents reported by the local press.

Lam threatened to kill the whole family after learning through a biological test that he was not the father of Elvis Lam, the eight-year-old victim, the complaint said.

Teachers described Elvis as "quiet and kind" who would be missed greatly by his peers.

Lam also had a record of sexual assault and drug use with Edmonton police.