A catastrophic wildfire that has forced all 88,000 residents to flee Fort McMurray in Alberta, Canada has exploded tenfold in size, cutting off evacuees in camps and shelters north of the city.

The out-of-control blaze has burned down entire neighbourhoods of Fort McMurray in Canada's energy heartland and forced a precautionary shutdown of some oil production, driving up global oil prices.

Three days after the residents were ordered to leave Fort McMurray, firefighters on Thursday were still battling to protect homes, businesses and other structures from the flames. More than 1600 structures, including hundreds of homes, have been destroyed.

Although the cause of the fire was unknown, officials said tinder-dry brush, low humidity and hot, gusting winds left crews unable to stop the flames.

The blaze, which erupted on Sunday, grew from 7500 hectares on Wednesday to some 85,000 hectares on Thursday.

"What people in that region have gone through in the last couple of days is literally hell on earth," Rona Ambrose, leader of the opposition Conservative Party and an Albertan, fighting back tears as she addressed the Canadian Parliament in Ottawa.

Fire has intermittently blocked the only route south toward major cities, so thousands of evacuees fled north toward oil camps and a few small settlements but found themselves with no road route out.

Some 20,000 people were stranded in oil camps, makeshift shelters and on roadsides north of the city where the flames cut them off from Fort McMurray. Most of Alberta's oil sands facilities are north of the city and not in the path of the flames.

Evacuee Jason Blair said he only had enough time to grab a few belongings before driving north to a Canadian Natural Resources Ltd facility.
"For some reason I really wanted my son's first pair of shoes," he told CBC television.

An airlift of evacuees began from oil facility airstrips on Thursday.

Canadian Natural Resources said it airlifted about 2600 people over the last 24 hours to Edmonton and Calgary, including its own workers, to make room for more evacuees.

The winds gave the city a brief reprieve on Thursday by driving the fire to the southeast, away from populated areas.

But officials warned that the unpredictable weather could shift again.

The winds pushed flames toward the local airport, which suffered minor damage and was open for limited non-commercial operations, officials said.

At least 640,000 barrels per day of crude output is offline, according to Reuters calculations, roughly 16 per cent of Canada's crude production.The outage is expected to climb as major players in the region cut production.

The forecast has called for cooler temperatures and a possibility of rain, offering hope that controlling the blaze could become easier.

Authorities said there had been no known casualties from the blaze itself, but fatalities were reported in at least one vehicle crash along the evacuation route.