REYKJAVIK, Iceland (AP) -- Iceland raised its aviation alert to red Saturday as a subglacial eruption began at the restless Bardarbunga volcano, which has been rattled by thousands of earthquakes in the past week, the country's Meteorological Office said.
Seismic data indicated that lava from the volcano was melting ice beneath the Vatnajokull glacier, Iceland's largest, Met Office volcanologist Melissa Pfeffer said.
She said it was not clear when, or if, the eruption would melt through the ice - which is between 100 to 400 meters (330 to 1,300 feet) thick - and send steam and ash into the air.
The eruption led Iceland to raise its aviation alert level to red, indicating an eruption that could cause "significant emission of ash into the atmosphere." Red is the highest alert warning on a five-point scale.
Aviation authorities declared a no-fly zone around the volcano but did not shut Icelandic airspace.