THIS terrifying video shows the moment tourists run for their lives as the mammoth Mount Etna erupts behind them.

Groups of hikers were on the volcano’s slopes when it began spewing smoke and hot ash, with some just metres from the mouth forced to flee urgently.

Long lines of tourists could be seen snaking down the mountainside in the shadow of an enormous growing black cloud.

“Very intense and almost continuous” eruptions were reported from the Sicilian stratovolcano – Europe’s highest tinderbox.

Part of the southeastern crater is thought to have collapsed into the bubbling magma setting off the eruption.

A lava fountain has then sent boiling rock, ash, and the poisonous gas sulphur dioxide spewing from Etna’s mouth, visible for miles.

The cloud is now 4miles high – but it is slowly moving northwest and away from the nearby city of Catania.

Despite this the Volcanic Ash Advisory Center Toulouse (VAAC) has issued a code red for flights due to the eruption.

A code red means that there is a “significant” amount of ash in the atmosphere.

Only a small number of flights at Catania airport have been delayed as authorities respond to the safety challenge.

Italian civil aviation is yet to close any airspace.

Eruptions previously around the world have seen planes grounded for days due to risks posed by volcanoes.

Tourists on the fabled mountain captured the moment the eruption happened and the thick grey plume of smoke and ash rushed into the sky.

Other sightseers could be seen running for their lives as their holiday turned into a nightmare.

A terrifying volcanic tremor was felt just moments before the eruption.

The tremor began at roughly 10pm last night before reaching a peak three hours later in the middle of the night.

It was localised at an altitude of 1.7miles below the crater area.

They explained that an ash cloud made predominantly of water and sulphur dioxide was “drifting towards the south west”.

Italy’s National Institute of Geophysics and Volcanology said: “Over the past few hours, the activity flagged in the previous statement issued at 4.14am (3.14am BST) has carried on with strombolian explosions of growing intensity that, at the moment, are of strong intensity and nearly continuous.”

They explained that explosive activity from the Southeast Crater has “moved to a lava fountain,” adding that the “volcanic tremor has reached very high values”.

In the past, Etna’s eruptions have caused nearby towns to be covered in black volcanic ash.

The mountain is one of the most active volcanoes in southern Italy, with the last eruption occurring in May.

In February, Mount Etna turned into a fiery peak as hot lava spewed from the erupting volcano.

Marco Bassot, who has 416,000 Instagram followers, captured the moment on camera.

Snowboarder Marco said: “This fracture started some days ago and created a huge, intense and impressive lava flow for more than 1,000 meters.

“I’ve seen many things in my 40 years of life but riding side by side of a flowing river of lava is one of the most special, impressive, and breathtaking experiences I’ve ever lived.”