A volcano erupted in southwest Iceland on Sunday, posing an immediate threat to a nearby fishing town that had been evacuated over fears of an outbreak, authorities said.

Early-morning live streams from the site showed fountains of molten rock spewing from fissures in the ground, the bright orange lava flow glowing against the dark sky.

The eruption began north of the town of Grindavik, which on Saturday was evacuated for a second time over fears that an outbreak was imminent amid a swarm of seismic activity, authorities said.

Iceland in recent weeks sought to build barriers of earth and rock to prevent lava from reaching Grindavik, but the latest eruption appeared to have penetrated the defences.

“According to the first images from the Coast Guard’s surveillance flight, a crack has opened on both sides of the defences that have begun to be built north of Grindavík,” the Icelandic Meteorological Office said in a statement.

“Lava is now flowing towards Grindavík. Based on measurements from the Coast Guard’s helicopter, the perimeter is now about 450 metres (1,500 feet) from the northernmost houses in the town,” it added.

It was the second volcanic eruption on the Reykjanes peninsula in southwest Iceland in less than one month and the fifth outbreak since 2021.

Last month, an eruption started in the Svartsengi volcanic system on Dec 18 following the complete evacuation of Grindavik’s 4,000 residents and the closing of the Blue Lagoon geothermal spa, a popular tourist spot.

More than 100 Grindavik residents had returned in recent weeks before Saturday’s renewed evacuation order, according to local authorities.

Iceland’s civil protection agency on Sunday said it had raised its alert level to “emergency”, the highest on a three-level scale, signalling an event had begun that could cause harm to people, communities, property or the environment.

Lying between the Eurasian and North American tectonic plates, two of the largest on the planet, Iceland is a seismic and volcanic hot spot as the two plates move in opposite directions.