STOCKHOLM, Aug 27 (Reuters) - Two earthquakes measuring more than magnitude 5 hit Iceland's Bardarbunga volcano overnight and overall seismic activity remained high, the country's Meteorological Office said on Wednesday.
The rumblings at Iceland's largest volcano system have raised worries of an eruption which could spell trouble for air travel. In 2010, an ash cloud from the Eyjafjallajokull volcano closed much of Europe's airspace for six days.
"During the night we have had three larger events, two of them in the Bardarbunga caldera. Those were 5.2 and 5.3, and very similar to the events that we have seen there before," said Palmi Erlendsson, a geologist at the Met Office.
He said there had also been a 4.5 magnitude quake at the nearby Askja volcano. The night before saw a magnitude 5.7 quake -- the biggest earthquake yet at Bardarbunga.
On Sunday, Iceland lowered its warning code for possible volcanic disruption to the aviation industry to orange from red, after concluding that seismic activity had not led to a volcanic eruption under the glacier.
Red alert -- the highest warning level -- indicates an eruption is imminent or underway, with a significant emission of ash likely. (Reporting by Sven Nordenstam; Editing by Crispian Balmer)