Rivers of lava have raced down the volcano and exploded high into the air overnight on the Spanish island of La Palma and the airport was closed as the ongoing eruption intensified and entered its most explosive phase so far.

Since it began erupting last Sunday on the small island in the Atlantic, the Cumbre Vieja volcano has spewed out thousands of tonnes of lava, destroyed hundreds of homes and forced the evacuation of nearly 6000 people.

Authorities said on Saturday the 160 people moved from three more towns on Friday would not be able to return to their homes to retrieve their belongings because of the “evolution of the volcanic emergency”.

Experts said the volcano had entered a new explosive phase.

Big bang fears

“Volcanic surveillance measurements carried out since the beginning of the eruption recorded the highest-energy activity so far during Friday afternoon,” emergency services said in a statement on Friday evening.

Spanish airport operator Aena said on Saturday the island’s airport had been closed.

“La Palma airport is inoperative due to ash accumulation. Cleaning tasks have started, but the situation may change at any time,” it tweeted.

La Palma, with a population of over 83,000, is one of an archipelago making up the Canary Islands.

On Friday, firefighters retreated from clean-up work in the town of Todoque, airlines cancelled flights, and authorities evacuated the towns of Tajuya, Tacande de Abajo and the part of Tacande de Arriba that had not already been evacuated after a new vent opened up in the flank of the volcano.

Videos shared on social media showed a massive shock wave emanating from the eruption site on Friday.

No serious injuries or fatalities have been reported in the volcano’s eruption, but about 15 per cent of the island’s economically crucial banana crop could be at risk, jeopardising thousands of jobs.

-AAP