Smoke rises during the wildfire in Kelowna; people line up outside of a local school to register to be evacuated in Yellowknife, Canada, on Thursday. Reuters

Since authorities in the Northwest Territories issued the city-wide evacuation order late on Wednesday, long lines of cars have snaked along the lone highway connecting the area to Alberta province to the south ahead of the 12:00 pm (1800 GMT) limit.

About 1,500 people have so far left Yellowknife, the regional capital, by plane, with an increased number of flights scheduled on Friday to evacuate more of the city's 20,000 residents. The nearest evacuation center is 1,150 kilometres away, in Alberta, where several sites have been set up.

"We're going to keep going until we have the population of Yellowknife out," emergency services official Jennifer Young told a briefing.

Air Canada pilot Chad Blewett, who flew one of the first relief flights out of the lakeside city, told public broadcaster CBC that Yellowknife "is pretty empty already."

The stragglers, he said, were mostly essential workers "building fire breaks and working with airlines (to facilitate evacuations)."

Crews have scrambled to erect defenses as the flames approach Yellowknife, while water bombers have been seen flying low over the city.

Strong winds over the next two days will send the fire, already within just a few kilometers of the city's perimeter, "in directions we don't want," Northwest Territories' fire information officer Mike Westwick said late on Thursday.

Several military aircraft have already been dispatched, along with more than 120 soldiers to help beat back the flames.

Massive evacuation

In what had already been declared the Northwest Territories' largest-ever evacuation, the emptying of Yellowknife now means half the population of the near-Arctic territory will soon be displaced.

Several towns and Indigenous communities were also already under evacuation orders.

Prime Minister Justin Trudeau interrupted his summer vacation to convene an incident response group late on Thursday. Officials were to provide an update at midday.

In Canada's westernmost province of British Columbia, evacuation orders were also put in place for areas near Kelowna, as a different fire threatened the city of around 150,000.

Nearly 2,500 homes and businesses on its west side were ordered evacuated, while another 4,800 were advised to be ready to leave on a moment's notice.

"The fire remains very active and unpredictable," the British Columbia emergency operations center warned.