Livestreams from the area showed fountains of molten rock soaring from fissures in the ground after authorities had warned for weeks that an eruption was imminent on the Reykjanes peninsula just south of Iceland's capital Reykjavik.
"Warning: An eruption began in Reykjanes," the Icelandic Meteorological Office said on its website, while Reykjavik's nearby Keflavik Airport's website showed it remained open both for departures and arrivals.
Iceland, which is roughly the size of the U.S. state of Kentucky, boasts more than 30 active volcanoes, making the north European island a prime destination for volcano tourism - a niche segment that attracts thousands of thrill seekers.
In 2010, ash clouds from eruptions at the Eyafjallajokull volcano in the south of Iceland spread over large parts of Europe, grounding some 100,000 flights and forcing hundreds of Icelanders to evacuate their homes.
Volcanic outbreaks in the Reykjanes peninsula are so-called fissure eruptions, which do not usually cause large explosions or significant dispersal of ash into the stratosphere.
However, scientists fear they could continue for decades, and Icelandic authorities have started building dykes to divert burning lava flows away from homes and critical infrastructure.
The volcano last erupted in early February, cutting off district heating to more than 20,000 people as lava flows destroyed roads and pipelines, while an outbreak in January burned to the ground several houses in a fishing town.
Located between the Eurasian and the North American tectonic plates, among the largest on the planet, Iceland is a seismic and volcanic hot spot as the two move in opposite directions.
(Reporting by Nordic newsrooms, editing by Terje Solsvik and Alexander Smith)
