A volcanic eruption at Grimsvotn has hit Iceland on May 21, sending a huge bubbling mass of ash and smoke, accompanied by multiple earthquakes.

The ash cloud from the eruption rose to 20km/12 miles, and is so far 10 times larger than the 2004 eruption, and the strongest in Grímsvötn for 100 years.

Grimsvotn, which sits at the heart of Iceland's biggest glacier, is known as the most active volcano in Iceland and has erupted 9 times between 1922 and 2004.

Meanwhile, airlines began cancelling flights to Britain late on Monday as the ash cloud from the Icelandic volcano reaching its airspace, although experts expected no repeat of travel chaos from an eruption a year ago.

The ash cloud from the erupting Grimsvotn volcano in Iceland is expected to disrupt U.K. flights from Tuesday, the Civil Aviation Authority said.

The latest Met Office predictions showed the plume of ash would cover the Irish Republic, Northern Ireland, Scotland and parts of northern Britain.

Almost a year-ago, Eyjafjallajökull volcano erupted in Iceland, resulting in a shutting down of airports in the region that stranded millions of passengers.