Parks Canada officials have issued an evacuation alert for Waterton Lakes National Park because of a massive out-of-control wildfire burning just south of the townsite.

The fire is just five kilometres south of the townsite and it's approaching Upper Waterton Lake. It's approximately 700 hectares in size.

Officials say the situation is stable at the moment, but anyone in the area needs to be prepared to leave if it suddenly gets more dangerous.

Aircraft are being used to help bring the blaze under control and slow its eastward motion towards Waterton Lakes.

Once the evacuation order is given, everyone will have one hour to get out.

The alert comes just under a year since a large wildfire ripped through the park and townsite, destroying the visitor centre and a handful of homes. 190 square km of the park was damaged and 80 percent of its hiking trails.

(With files from the Canadian Press)