"We estimate that no one is in danger in the area but we have started an evacuation plan and between 500 and 600 people are being evacuated" Sigurgeir Gudmundsson of the Icelandic civil protections department told AFP.

RUV public radio reported that three Iceland-bound Icelandair flights, out of Boston, Orlando and Seattle, had been ordered to turn back to the United States.

It said the eruption took place shortly after midnight and that local residents were being evacuated because of the risk of flooding caused by melting glacier waters.

"Ash has already begun to fall in Fljotshlid and people in the surrounding area have reported seeing bright lights emanating from the glacier," RUV said on its website, advising area residents to follow developments closely.

"There is currently no sign of flooding, but it could be imminent according to experts," it added.

"It is not clear exactly where the eruption is taking place but it is being investigated."

A volcano in the area of the Eyjafjallajoekull glacier last erupted in 1821 and 1823.

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