Authorities in Spain's Canary Islands told residents on the western coast of La Palma to lock down and seal doors and windows with tape and wet towels to ward off toxic gases spewed by lava from the Cumbre Vieja volcano.

Incandescent lava gushing from the volcano for 10 days poured down a cliff into the sea early on Wednesday in the Playa Nueva area, sending big clouds of white steam and toxic gases billowing into the air.

By dawn on Wednesday, Reuters video showed a pyramid of red hot lava emerging above the Atlantic Ocean waterline.

The Canary Islands' emergency service urged those outdoors less than 3.5 kilometres from the stricken area to immediately find a safe place to shelter. No injuries have been reported.

The emergency services also recommended people "protect breathing tracts with a wet cloth covering mouth and nose".

Lava has been flowing down Cumbre Vieja's western flank toward the sea since Sept. 19, swallowing almost 600 houses and banana plantations in La Palma, which neighbours Tenerife in the Canary Islands archipelago off the North African coast.

Thousands of people have been evacuated and three coastal villages were locked down on Monday in anticipation of the lava reaching the sea.

Spain classified La Palma as a disaster zone on Tuesday, a move that will trigger financial support for the island.