A volcano in south-western Iceland has erupted for the third time since December, sending jets of lava into the sky and triggering the evacuation of the Blue Lagoon spa, one of the island nation’s biggest tourist attractions.

The eruption began at about 0600 GMT along a three-kilometre (nearly two-mile) fissure north-east of Mount Sundhnukur, the Icelandic Meteorological Office said.

The event is taking place about four kilometres (two-and-a-half miles) north-east of Grindavik, a coastal town of 3,800 people that was evacuated before a previous eruption on December 18.

The Icelandic Meteorological Office said that lava was flowing to the west and there was no immediate threat to Grindavik or to a major power plant in the area.

Civil Defence officials said that no-one was believed to be in the town at the time of the eruption, Icelandic national broadcaster RUV reported.

“They weren’t meant to be, and we don’t know about any,” Vioir Reynisson, the head of Iceland’s Civil Defence, told Icelandic national broadcaster RUV.

The Civil Defence agency said that lava was heading for a pipe that supplies communities on the peninsula with hot water from the Svartsengi geothermal plant.

Authorities asked people to use hot water sparingly, as workers rushed to lay an underground water pipe as a back-up.

The nearby Blue Lagoon thermal spa was closed when the eruption began and all the guests were safely evacuated, RUV said.

A stream of steaming lava later spread across the exit road from the spa.

The Icelandic Met Office earlier this week warned of a possible eruption after monitoring a build-up of subsurface magma for the past three weeks.

The amount of magma or semi-molten rock that had accumulated was similar to the amount released during an eruption in January.

Hundreds of small earthquakes had been measured in the area since last Friday, capped by a burst of intense seismic activity about half an hour before the latest eruption began.

Dramatic video from Iceland’s coast guard shows fountains of lava soaring more than 50 metres (165ft) into the darkened skies.

A plume of vapour is rising about three kilometres (one-and-a-half miles) above the volcano.

This is the third eruption since December of a volcanic system on the Reykjanes Peninsula, which is home to Keflavik, Iceland’s main airport.

There was no disruption reported to the airport on Thursday.

Iceland, which sits above a volcanic hot spot in the North Atlantic, averages an eruption every four to five years.

The most disruptive in recent times was the 2010 eruption of the Eyjafjallajokull volcano, which spewed huge clouds of ash into the atmosphere and led to widespread airspace closures over Europe.

Grindavik, about 50 kilometres (30 miles) south-west of Iceland’s capital Reykjavik, was evacuated in November when the Svartsengi volcanic system awakened after almost 800 years with a series of earthquakes that opened large cracks in the earth between the town and Sylingarfell, a small mountain to the north.

The volcano eventually erupted on December 18, sending lava flowing away from Grindavik.

A second eruption that began on January 14 sent lava towards the town.

Defensive walls that had been bolstered since the first eruption stopped some of the flow, but several buildings were consumed by the semi-molten flow.