- The new fissure opened up near Sundhnuksgigar on the Reykjanes peninsula, the fifth eruption in the area since December.
- The Icelandic Meteorological Office (IMO) said the fissure was longer than 2.5km (1.5 miles) and was continuing to grow.
Another volcanic eruption has begun in south-west Iceland, forcing the evacuation of the famous geothermal Blue Lagoon spa and the small fishing town of Grindavik.
The new fissure opened up near Sundhnuksgigar on the Reykjanes peninsula, the fifth eruption in the area since December.
The Icelandic Meteorological Office (IMO) said the fissure was longer than 2.5km (1.5 miles) and was continuing to grow.
Footage from the site shows a wall of molten rock shooting up to a height of 50m, and huge plumes of ash covering most of the sky.
Officials also reported "intense earthquake activity" prior to Wednesday's eruption.
A state of emergency has been declared - a step that has been taken following all recent eruptions.
According to state broadcaster RUV, power had been cut off to the largely abandoned town of Grindavik to protect a high-voltage line that was at risk.
The nearby Svartsengi power plant, which provides electricity and water to thousands of people on the peninsula, has also been evacuated.
Barriers have been built up around the facility, as well as Grindavik and the Blue Lagoon, to try to protect them from magma flows caused by the ongoing eruptions.
Keflavik international airport said it was operating as usual and did not expect to be affected.
Most of the 4,000 residents of Grindavik were permanently evacuated in November, prior to the eruptions in December, January, February and March.
Lava flowed into its streets during the January eruption, engulfing three homes.
A few residents had since returned to live in neighbourhoods less at risk from lava flow, but officials said they were evacuated again on Wednesday when the magma intrusion began to flow closer to Grindavik.
Local media reported that three people had refused to leave.
Iceland has 33 active volcano systems and sits over what is known as the Mid-Atlantic Ridge, the boundary between two of the largest tectonic plates on the planet.
The last time the Reykjanes Peninsula had a period of volcanic activity was 800 years ago - and the eruptions continued for decades.
This is now the eighth eruption since 2021, and scientists believe the area is entering a new volcanic era that could last for decades or even centuries.