Firefighters battle 'unprecedented' wildfires in Canada

Firefighters have faced a gruelling uphill battle against wildfires in Canada's Nova Scotia province, including one threatening the suburbs of Halifax.

Federal help was coming to the Atlantic province, officials said on Wednesday, along with firefighters from the United States.

"We're in a crisis in the province, and we want, and we need, and we will take all the support we can get," Nova Scotia Premier Tim Houston told a news conference.

"These fires are unprecedented."

Already, additional kits have been shipped in from Ontario, and a dozen water bombers from neighbouring regions and the Coast Guard joined efforts to douse the flames.

Houston said he has also asked for the military to help out.

Prime Minister Justin Trudeau called the wildfires "heartbreaking" and vowed unlimited support.

As of Wednesday, 14 wildfires were burning in Nova Scotia, including three out of control.

They've so far destroyed or damaged more than 200 structures, but no injuries have been reported.

One couple described to public broadcaster CBC having lost their home and childcare business.

"That's my life," a tearful Terri Kottwitz said. Others said they saw trees on fire in their backyard as they fled.

Air polluted in US

Smoke from the wildfires blew down the Atlantic coast, prompting air quality alerts for the US state of New Jersey and parts of Pennsylvania, including Philadelphia.

"Sensitive groups should minimise strenuous outdoor activities," the NWS in Philadelphia said in a Facebook post along with a photograph of a hazing orange sun.

David Meldrum of the Halifax Regional Fire and Emergency, pointing to record temperatures forecast this week, warned of "a prolonged operation" to bring under control a large fire northwest of the city that has displaced more than 16,000 residents.

"People are understandably tired, frustrated and frightened," said Halifax Mayor Mike Savage.

Houston announced late on Tuesday a ban on all activities in Nova Scotia forests, including hiking, camping, fishing, hunting, the use of off-road vehicles and logging.

"For God's sake, stop burning. Stop flicking cigarette butts out of the car window. Just stop it. Our resources are stretched incredibly thin right now fighting existing fires," he pleaded.