Witnesses described seeing thick plumes of smoke "like a volcano had erupted" blowing across the water from woodland above the villages of Bannavie and Corpach, opposite Fort William, as a fierce blaze ripped through trees and shrubland.
The area is one of the few in Scotland to have avoided the recent snowfalls, with local residents describing how weeks without rain had left the surrounding landscape bone dry and "ready to burn".
The cause of the fire remains unknown but it coincides with the end of the season when moorkeepers are allowed to burn heather to keep it healthy and prevent it growing out of control. However, it could also have been started by someone stubbing out a cigarette.
A spokesman for Highlands and Islands Fire and Rescue said firefighters had been dispatched on seven appliances and would be working through the night to keep the blaze under control and stop it spreading to residential areas.
He said they had been called to the Fort William area around 4pm yesterday but had also tackled grass and hill fires as far away as Skye.
Firefighters were last night stretched along a route from the B8004 near Fort William to Corpach, one-and-a-half miles away, so that they could douse flames at the perimeter of the blaze. However, it was too dangerous to enter the forest until first light today.
The spokesman said: "Firefighters are tackling a blaze from along the roadway but we are not committing them any further due to the darkness and the obvious dangers that that entails. The fires are spread across a five-kilometre area. We have water supplies around the perimeter and firefighters will be working through the night to prevent the fire spreading to residential areas.
"Police are in attendance, and there are no plans to evacuate anyone at the moment but we will work with the police on that."
Local resident Iain Ferguson said he had first become aware of the blaze at around 5pm on Sunday, March 31.
He said: "There are large pillars of smoke blowing towards us from the woodland over Banavie and Corpach. Earlier it was like a volcano had erupted, and the wind has been fanning the flames.
"We haven't had rain for about five weeks - the ground is bone dry. While everywhere else was worrying about snow we were enjoying blue skies and sunshine, but everything is like tinder and just ready to go."
Tina Cuthbertson, of the Smiddy Bunkhouse in Corpach, said she could see the flames spread over Druim Fada hill from her window.
"There are enormous flames and everything is tinder dry at the moment. The fire is getting fairly close to the houses. I feel fairly safe - for now."
Councillor Thomas MacLennan, of Fort William and Ardnamurchan ward, said: "The fire raced across the hillside with the help of a little wind. I am around four miles away and I can see the fire quickly. We have had a number of fire in the western Highland but I have never seen a fire like this in Fort William, so close to homes."
He said the fire was most intense around the Corpach area. "There is a lot of foliage, forest and scrub there, a lot of precipitation in that area and very little rain," he added.
Councillor MacLennan, who estimated the flames were around 30ft high, said that firefighters had been called in from across the Highlands to deal with the fire as it licked around Fort William.
He said: "I had been due at the Ardnamurchan Community Council meeting but it was cancelled as a few of the members were called to deal with the fire. That is almost 70 miles away from Fort William."
Firefighters have tackled blazes over the weekend, with around a million square metres of heath, grass and trees burned in dozens of wildfires, threatening properties and destroying electricity posts and fences.
Amongst the areas affected were Eilean Shona, a remote tidal island in Loch Moidart around 40 miles west of Fort William, and near the village of Poolewe in Wester Ross.