Grindavik (Iceland) (AFP) -
Glowing red lava spewed Saturday from a volcano that has erupted near Iceland's capital Reykjavik after being dormant for more than 900 years.
But officials said the eruption was small and did not appear to represent a danger to people.
Dramatic images filmed by a coast guard helicopter showed streams of red lava bubbling and flowing out of a fissure in a valley in Geldingadalur, close to Mount Fagradalsfjall on the Reykjanes peninsula in southwestern Iceland.
As the lava continued to flow on Saturday, clouds of blue gas were also swirling from the site, located just 40 kilometres (25 miles) from the capital and near the Blue Lagoon geothermal spa, a popular tourist destination.
The eruption occurred on Friday around 2045 GMT, lighting up the night sky with a crimson glow, after hundreds of small earthquakes shook the area.
While Iceland's Keflavik International Airport and the small fishing port of Grindavik are just a few kilometres away, the zone is uninhabited and the eruption did not appear to present any danger.
From Grindavik, steam could be seen rising from the area in between rain showers, an AFP reporter said.
'The eruption is considered small,' the Icelandic Meteorological Office (IMO), which monitors seismic activity, said in a statement Saturday.
It said the 'eruption fissure' is estimated to be about 500-1,000 metres (1,640 - 3,280 feet) long.
The lava, it added, is estimated to be less than one square kilometre (0.4 square miles) in size.
'There is little eruption activity in the area,' the IMO said.
The eruption took place in the Krysuvik volcanic system, which does not have a central volcano, about five kilometres inland from the southern coast.
- Dormant for 900 years -
There were no reports of ash fall, although tephra -- solidified magma rock fragments -- and gas emissions were to be expected.
The public has been advised to stay away from the scene and access to the area has been blocked off.
Police ordered residents living east of the volcano to close their windows and stay indoors due to the risk of possible gas pollution carried by the wind.
Scientists were measuring gas emissions but no information had been disclosed by Saturday morning.
Gases -- especially sulphur dioxide -- can be elevated in the immediate vicinity of a volcanic eruption, and may pose a danger to health and even be fatal.
Pollution can exceed acceptable limits, even far away, depending on the winds.
Eruptions in the region are known as effusive eruptions, where lava flows steadily out of the ground, as opposed to explosive ones which spew ash clouds high into the sky.
The Krysuvik system has been inactive for the past 900 years, according to the IMO, while the last eruption on the Reykjanes peninsula dates back almost 800 years and lasted about 30 years, from 1210 to 1240.
But the region has been under increased surveillance for several weeks after a 5.7-magnitude earthquake was registered on February 24 near Mount Keilir on the outskirts of Reykjavik.
Since then an unusual number of smaller tremors -- more than 50,000 -- had been registered, the highest number since digital recordings began in 1991.
The seismic activity gradually moved several kilometres southwest after the quake, concentrating around Mount Fagradalsfjall, where magma was detected just one kilometre under the Earth's surface in recent days.
Seismic activity had however subsided in the past few days.
- Land of fire and ice -
Iceland has 32 volcanic systems currently considered active, the highest number in Europe. The country has had an eruption every five years on average.
The vast island near the Arctic Circle straddles the Mid-Atlantic Ridge, a crack on the ocean floor separating the Eurasian and North American tectonic plates.
The shifting of these plates is in part responsible for Iceland's intense volcanic activity.
The most recent eruption was at Holuhraun, beginning in August 2014 and ending in February 2015, in the Bardarbunga volcanic system in an uninhabited area in the centre of the island.
That eruption did not cause any major disruptions outside the immediate vicinity.
But in 2010, an eruption at the Eyjafjallajokull volcano sent huge clouds of smoke and ash into the atmosphere, disrupting air traffic for more than a week with the cancellation of more than 100,000 flights worldwide which left some 10 million passengers stranded.