Iceland says it is closely monitoring its most active volcano after a glacier broke off, which could trigger a new eruption.
Grimsvotn volcano lies beneath the Vatnajokull glacier - Europe's largest glacier - in a remote, uninhabited area of central Iceland.
The Icelandic Meteorological Office (IMO) said that seismic activity at the Grimsvotn volcano in recent months has been higher than normal and a strong ice flow has formed near the volcano.
Authorities have raised the alert level for the Grimsvotn volcano to yellow, warning the aviation industry of a possible volcanic eruption.
The most recent eruption of the Grimsvotn volcano in 2011 sent ash into the atmosphere, affecting air traffic with around 900 flights cancelled.
Iceland's most recent volcanic eruption took place less than a month ago south of the capital Reykjavik, forcing the evacuation of 4,000 residents of the town of Grindavik.