Wildfire near Madrid sparks mass evacuations as inferno rages out of control

WATCH: Four British nationals feared dead in burnt-out car as 'ferocious' wildfires sweep across southern Spain

Tens of thousands have fled their homes as Spain declared a national emergency over the 'worst wildfire in Madrid's history'

Spain has declared a national emergency after a massive wildfire west of Madrid forced at least 30,000 people to flee their homes.

The blaze, described by Madrid regional president Isabel Díaz Ayuso as the "worst fire in the history of the region", has burned through around 15,000 hectares across Madrid and neighbouring Avila province.

Officials warned the inferno is now beyond firefighters' ability to contain after three separate wildfires merged into a single front, fuelled by soaring temperatures, strong winds and tinder-dry conditions.

More than 60,000 people have been directly affected, while a further 20,000 residents remain under lockdown around 50 kilometres west of the Spanish capital.

The fire continues to advance towards the municipalities of Robledo de Chavela and Fresnedillas de la Oliva.

Carlos Novillo, Madrid's regional emergency chief, warned the situation remained critical.

"The wildfire is at its peak and is currently beyond the capacity of firefighters to contain," he told reporters.

"It's not possible to attack the fire in that area, so defensive measures are being taken."

Spain's Military Emergency Unit has been deployed to protect communities around the historic town of El Escorial as crews battle to halt the fire's advance.

Officials warned the inferno is now beyond firefighters' ability to contain after three separate wildfires merged into one

Authorities are also racing to stop the Madrid blaze from merging with a separate wildfire in neighbouring Avila province, where almost 9,000 hectares have already been destroyed.

Interior Minister Fernando Grande-Marlaska said officials were doing "everything we can" to prevent the two fires joining together.

The speed of the blaze has shocked local communities.

Arturo Varas Gonzalez, mayor of El Tiemblo, said flames travelled around 20 kilometres in less than 30 minutes.

"It was horrific," he told broadcaster laSexta.

Authorities are also racing to stop the Madrid blaze from merging with a separate wildfire in neighbouring Avila province

One person has been arrested by Spain's Civil Guard in connection with the Burgohondo wildfire, with investigators examining whether heavy machinery sparked the blaze during a period of fire restrictions.

Eight municipalities have now been evacuated, including Chapineria, Navas del Rey, Colmenar del Arroyo, Aldea del Fresno, Navalagamella and Zarzalejo.

Several more towns, including San Martín de Valdeiglesias, Pelayos de la Presa and Villa del Prado, remain under lockdown.

Francisco Martin, the Spanish Government's delegate in Madrid, warned the situation could deteriorate further.

"Embers are flying for miles and the fire is jumping great distances," he said.

Among those forced to flee was 86-year-old Ecologio Cabrera.

Speaking from an evacuation centre in Vilamanta, he told AFP: "If you don't run from it and you try to face it, it devours you."

His family had tried to protect their home with garden hoses before firefighters ordered them to leave.

"I have never experienced anything like this," he said.

The crisis has spread beyond Spain, with wildfires in southwest France forcing more than 110,000 people from their homes.

President Emmanuel Macron has deployed the armed forces to help firefighters as flames threaten Bordeaux.

Spanish Prime Minister Pedro Sanchez, who warned on Friday the country was "living through a dramatic situation", is expected to visit an emergency coordination centre on Saturday.