REYKJAVIK, Iceland — Iceland’s Bardarbunga volcano began erupting Saturday under the ice of Europe’s largest glacier, prompting the country to close the airspace over the volcano.

Thousands of small earthquakes have rattled the volcano, located deep beneath the Vatnajokull glacier, in the last week. Seismic data indicated that magma from the volcano was melting ice beneath the glacier’s Dyngjujokull icecap, Meteorological Office vulcanologist Melissa Pfeffer said.

The remote area, 200 miles east of the capital of Reykjavik, is uninhabited.

The Civil Protection Department said scientists flew over the ice cap Saturday afternoon but saw no visible signs of the eruption on the surface of the glacier.

Still, authorities raised the country’s aviation alert to red – the highest level on a five-point scale – indicating the threat of “significant emission of ash into the atmosphere.”

Icelandic authorities declared a no-fly zone of 100 nautical miles by 140 nautical miles around the eruption as a precaution, but did not shut down air space over most of the island nation in the North Atlantic.

“All airports are open and flights are on schedule,” said spokeswoman Olof Baldursdottir.

A 2010 eruption of Iceland’s Eyjafjallajokul volcano produced an ash cloud that caused a week of international aviation chaos, with more than 100,000 flights canceled.

Pfeffer said it was not clear when, or if, the eruption would melt through the ice – which is 330-1,300 feet thick – and fling steam and ash into the air.