Floods force evacuation of downtown Calgary, Alberta

At least three people were killed by floodwaters that devastated much of southern Alberta, leading authorities to evacuate the western Canadian city of Calgary's entire downtown.

Prime Minister Stephen Harper called the level of flooding "stunning" and said officials did not know yet if it would get worse, but said the water had peaked and stabilised and noted that the weather had got better.

Overflowing rivers washed out roads and bridges, soaked homes and turned streets into dirt-brown waterways around southern Alberta.

Royal Canadian Mounted Police Sergeant Patricia Neely said three were dead and two bodies had been recovered.

The two men had been seen floating lifeless in a river on Thursday, she said.

Harper, a Calgary resident, said he never imagined there would be a flood of this magnitude in this part of Canada.