Icelandic authorities early Sunday registered the strongest earthquake so far at the Bardarbunga volcano in the south-east, where activity increased a week ago, and maintained a red alert warning for aviation.
The magnitude 5.3 earthquake was the largest seismic activity in the past week, and the largest at Bardarbunga since 1996, geophysicist Gunnar Gudmundsson at the Icelandic Meteorological Office told dpa.
Airspace in an area around the volcano, situated under the Vatnajokull glacier, remained closed. The red alert level designation - issued Saturday - means that an eruption is imminent or ongoing and that 'significant emission of ash' into the atmosphere is likely.
Hundreds of earthquakes have been registered during the past week.