Firefighters made gains in their battle against a vast wildfire on Tenerife on Sunday after better-than-expected overnight weather helped them keep the blaze from destroying homes on the Spanish holiday island, regional officials said.

The huge fire broke out late Tuesday in a mountainous northeastern area, quickly morphing into the Canary Islands' biggest-ever.

So far the blaze, which has a perimeter of 70 kilometres (43 miles), has burned through 8,400 hectares (20,800 acres), or just over four percent of Tenerife's overall surface area, forcing more than 12,000 people to flee their homes.

Despite expectations of a difficult night, things went "much better than expected", Canary Islands leader Fernando Clavijo said.

"We warned of a complex situation, with rising temperatures and wind... and it's true the night started very hard with many calls saying the fire was very close to people's homes," he told reporters Sunday morning.

But the firefighters "worked very intensively" and got through the night without losing a single home to the blaze, he said, describing it as "almost a miracle".

Montse Roman, technical head of the operation, said overnight operations were "mainly focused on defending infrastructure and homes on the northern flank of the fire", confirming there had "not been any more evacuations or confinement orders".

Some 20 aerial units were to join the battle against the blaze on Sunday alongside two more coordination units.

Late Saturday, Clavijo said the wildfire had so far displaced "a total of 12,279 people", citing figures from the Guardia Civil police.

- 'It will ruin us' -

As the fire spread down the mountainside towards the northern town of La Matanza de Acentejo on Saturday afternoon, Candelaria Bencomo Betancor, a farmer in her 70s, looked on in anguish.

"The fire is close to our farm, we've got trucks, vans, chickens, everything... it's a business that is going well but if the fire comes, it will totally ruin us," she told AFPTV, on the verge of tears.

"They have to do something because the fire is right there."

So far the fire has affected 11 municipalities on Tenerife, the largest of the seven Canary Islands, with the emergency services saying air quality was affected across much of the island "due to the smoke generated by the fire".

Pedro Martinez, who is in charge of firefighting efforts, said the blaze was "behaving like a sixth-generation wildfire" -- a term referring to a mega forest fire, and efforts to tackle the flames were being hampered by the huge clouds of smoke and the wind.

The blaze has generated a vast pillar of smoke that now stretches some eight kilometers into the air, rising far above the summit of Mount Teide, the volcano that towers over the island.

Spanish Prime Minister Pedro Sanchez is expected to visit the area on Monday.

Last year Spain suffered more than 500 blazes that destroyed more than 300,000 hectares, making it the worst-hit country in Europe, according to the European Forest Fire Information System (EFFIS).

So far this year, it has had 340 fires, which have ravaged almost 76,000 hectares, EFFIS figures show.