Media playback is unsupported on your device Media caption Footage of a roof colliding with a bridge in Bragg Creek, Alberta

At least three people have been killed and more than a 100,000 forced to flee their homes as floods triggered by torrential rain hit western Canada.

Officials have ordered the evacuation of the centre of Calgary, Alberta, after both rivers that flow through it, the Bow and Elbow, overflowed.

The floods have washed away roads and bridges, cut-off electricity and submerged hundreds of homes.

Canadian Prime Minister Stephen Harper toured flood-damaged areas on Friday.

He has promised federal assistance for those affected.

Royal Canadian Mounted Police Sgt Patricia Neely confirmed that three people were dead and two bodies had been recovered.

She said the bodies recovered are of two men found in the Highwood River near High River, about 40 miles (64km) south of Calgary, on Thursday.

Image copyright AP Image caption The Calgary Stampede grounds and Saddledome are flooded in Calgary Image copyright AP Image caption The flooding has forced the evacuation of the whole of central Calgary Image copyright AFP Image caption The Bow River's waters rose, along with the Elbow River's, washing away roads and bridges Image copyright AP Image caption Kevan Yaets, centre, and his cat Momo survived after escaping his submerged truck in High River, Alberta, on Thursday Image copyright Reuters Image caption Residents leave the Calgary's flooding downtown Image copyright AP Image caption Flood waters surround the hospital in Canmore, Alberta previous slide next slide

"This is incredible," said Mr Harper, a Calgary resident. "I don't think any of us have seen anything like this before. The magnitude is just extraordinary."

Alberta Premier Alison Redford warned residents should be prepared for more flooding downstream.

Communities further south were under total evacuation orders. Roughly half the homes in High River were flooded.

Swept away

While an estimated 230,000 people live and work in central Calgary, officials believed there would be few people to evacuate because many did not come to work on Friday.

Some 25 neighbourhoods in Calgary, a city of one million, had already been evacuated. An estimated 75,000 residents have been ordered out of their homes.

The floods come after a rainy week in Alberta, capped by 4in (10cm) of downpour on Thursday.

Military helicopters rescued about 30 people off rooftops in the Calgary area. At least 350 soldiers are being dispatched to the flood zone, according to the defence minister's office.

The mountain resorts of Banff and Canmore were left isolated after the Trans-Canada Highway was closed.

One resident of Canmore said he awoke in the middle of the night to a "kind of rumbling" sound and realised it was the nearby creek.

"At first it was just intense, pretty powerful, amazing thing to watch," Wade Graham told the Associated Press.

Media playback is unsupported on your device Media caption Canmore resident Sarah Pearson describes escaping across a bridge on a school bus

"As daylight came, it just got bigger and bigger and wider and wider, and it's still getting bigger and bigger and wider and wider."

"I watched a refrigerator go by. I watched a shed go by. I watched couches go by. It's insane," he added.

Calgary Mayor Naheed Nenshi said about 1,500 people went to emergency shelters while the rest were staying with family or friends.

Daniel Kilgallon, who is staying with his relatives after evacuating his flat, told the BBC: "The city has stopped functioning. Nobody can remember a flood like this ever happening here."

'An ocean'

Mr Nenshi warned that although the Elbow had crested, the city was not yet out of danger.

The Bow river, which Mr Nenshi said looked like "an ocean at the moment", is expected to remain at its current level for the next 12 hours.

Police have advised people against travelling to the city centre. Public transit there has been shut and schools are closed.

Officials said lions and tigers from the Calgary Zoo may need to be transferred to prisoner holding cells. Two zebras and two pigs have already been moved to a conservation centre.

The Saddledome, home to Calgary's professional hockey team, is also flooded with water levels rising to the stadium's 10th row.

Calgary resident Marshall Strong told the BBC several of his family members' homes were flooded.

"One farm that we went to had 60 cattle drowned in the fields," he said.

"It is truly unbelievable what has happened in such a short time. Calgary is a strong city and we have held it together better then we imagined."