A 17-year-old boy has been charged with four counts of first-degree murder after a school shooting in Canada.

Police in Saskatchewan province say they found two more bodies in a property in La Loche after arresting the suspect.

Earlier, the local mayor said his 23-year-old daughter, who taught at the school, was among the dead.

Speaking from the World Economic Forum in Davos, Switzerland, Canadian Prime Minister Justin Trudeau said the shooting was  "every parent's worst nightmare".

Chief Superintendent Maureen Levy said the motive for the attack, Canada's worst school shooting in decades, remains unclear.

In a statement Premier Brad Wall said: "Words cannot express my shock and sorrow at the horrific events today in La Loche."

"My thoughts and prayers are with all the victims, their families and friends and all the people of the community," he added.

Gun violence is relatively rare in Canada, which has stricter gun laws than the United States.

In 1989 a gunman, armed with a rifle and hunting knife, killed 14 female college students at Montreal's Ecole Polytechnique, before turning the gun on himself.