A major incident has been declared after two “rapidly developing and aggressive” moorland fires merged.
Greater Manchester Police said blazes on Winter Hill and Scout Road near Bolton have combined as a result of increasing wind speed.
The force told pedestrians and motorists to stay away from the scene.
Crews worked through the night tackling the flames, and Lancashire fire service said “full firefighting operations” resumed at 04:30 BST on Sunday.
It comes as crews from around the country have joined firefighters and the Army to deal with a separate fire at Saddleworth Moor in Greater Manchester, which started a week ago.
Along with the Winter Hill and Scout Road blazes, it has blanketed the region in smoke and ash. People in nearby areas have been asked to keep doors and windows closed.
The Winter Hill blaze, which started on Thursday near a major TV transmitter, is smouldering across a 1.9 sq miles (5 sq km) area.
A 22-year-old man, from Bolton, was arrested on Friday on suspicion of arson with intent to endanger life.
Lancashire fire service area manager Tony Cook said “very intensive firefighting” was taking place at the scene.
He said crews were doing shuttle runs in appliances to get water to the flames while others manually try to beat the fire out.
Fire break trenches are also being dug to try to protect local buildings and a helicopter has been dropping water to help douse the flames.
Greater Manchester Fire and Rescue Service said on Saturday it had 28 fire engines tackling the moorland fires.
There were approximately 120 personnel on the moors, split between seven areas of wildfire in Tameside and Winter Hill.
Assistant chief fire officer Dave Keelan said: “This is an exceptionally challenging time and I am proud of the hard work and brave commitment of our firefighters.”
About 100 soldiers from the 4th Battalion, Royal Regiment of Scotland, were sent from their Yorkshire barracks on Thursday to aid firefighters in Saddleworth for an initial 48-hour deployment.
Their presence has been extended until Monday afternoon following a request by Greater Manchester mayor Andy Burnham.