Iceland's Bardarbunga volcano remained poised to erupt Thursday, with an evacuation order still in force for an area to the north.

Authorities warned airlines Aug. 18 about increased seismic activity at Iceland's largest volcanic system. Ash from the eruption of Iceland's Eyjafjallajokull volcano in 2010 shut down much of Europe's airspace for six days.

The evacuation order by the country's civil protection agency came on Aug. 19.

The agency said the decision was a safety measure as it could not be ruled out that the seismic activity in Bardarbunga could lead to a volcanic eruption.

On Wednesday, about 1,000 earthquakes were detected in the Bardarbunga region, the largest quakes measuring around three in size.

All roads leading into the area around the volcano were closed earlier in the week and park rangers who live there during the summer and tourists have been removed.

Authorities say the area north of the glacier risks being hit by floods as an eruption in the volcano, which is under the ice cap of the Vatnajokull glacier in southeast Iceland, would melt vast amounts of ice.

The Icelandic Met Office on Monday raised its risk level to the aviation industry for an eruption to orange, which is the fourth level on a five-grade scale, after confirming magma movements less than 10 km from the surface.

The Vatnajokull National Park is more than 300 km from the capital Reykjavik and covers 14 per cent of Iceland.

The 2010 eruption at Eyjafjallajokull, a little over 100 km from the capital, affected more than 10 million air travellers and cost $1.7 billion US.