A rare wildfire on moorland east of Greater Manchester has spread smoke for miles and darkened skies in parts of one of Britain's most populated areas

A hundred soldiers and a military helicopter on Thursday joined firefighters battling a rare wildfire in northern England that could burn for weeks amid sustained hot weather, officials said.

The troops doubled the number of responders tackling the blaze on Saddleworth Moor east of Manchester, which broke out Sunday and led to the temporary evacuation of dozens of homes.

The , now covering seven square miles (18 sq kms) and being fuelled by peat, could spread if winds change direction, firefighters warned.

"We can see this being prolonged for days, if not weeks," said Tony Hunter, an assistant fire chief, noting controlling the blaze was "dependent on a downpour of rain".

He added: "If there is a change in wind to the opposite direction, it is a completely different picture then in terms of the fuel available to this fire."

No rain is forecast for the area for the rest of the week at least.

More than 100 firefighters have been working rolling 12-hour shifts to try to bring the wildfire, which is burning in six different locations, under control.

Firefighters worked until dusk Wednesday but suspended their efforts after deciding it was too dangerous to continue through the night.

An assessment at first light Thursday showed there was no "significant increase", Hunter added.

The soldiers will manage water lines, carry out fire beating and provide general support following a request for help from Manchester fire service.

RAF Wing Commander Tony Lane said: "We will make sure the soldiers are working alongside the fire and rescue personnel so they are going to be pairing up together."

The Chinook helicopter on standby can airlift heavy equipment, including a high-volume pump capable of pumping 7,000 litres of water a minute, to more inaccessible areas of the fire.

Fire officials say it is the worst wildfire in living memory to hit the area.

Smoke spreading for miles has darkened skies above swathes of Greater Manchester, one of the most populated in Britain.

The apocalyptic scene was visible from space as Nasa satellites picked up the plumes of smoke.

No injuries have been reported, but people living nearby have been advised to keep windows and doors closed by health officials.