Media playback is unsupported on your device Media caption Iceland's Foreign Minister Össur Skarphédinsson: "We are used to volcanos in Iceland"

Ash from a volcanic eruption in Iceland could begin to drift across the UK towards the end of the week, forecasters have said.

Aviation officials said there was no effect on UK airspace at present, but they were "monitoring the situation closely".

The Grimsvotn volcano is experiencing its largest eruption in 100 years.

It comes a year after ash from the Eyjafjallajokull eruption reached Europe, closing much of its airspace.

A spokesman for the Met Office, which runs Europe's Volcanic Ash Advisory Centre, said: "This is a very different situation to last April.

"The weather is much more changeable and there's a lot more uncertainty. There's no risk of the ash moving across the UK in the next day or so.

"But there is a possibility that we'll see some volcanic ash towards the end of the week."

Icelandic air traffic control has created a no-fly zone around the volcano, closed Keflavik airport, the country's main hub, and cancelled all domestic flights.

Image caption The Grimsvotn volcano in Iceland has sent a plume of smoke 12 miles into the air

Eurocontrol, the European air safety organisation, said no impact was expected on European airspace outside Iceland or on transatlantic flights for at least 24 hours.

A spokesman for the Civil Aviation Authority said: "We're monitoring the situation closely and working with our colleagues at National Air Traffic Services and the Met Office.

"There's no effect on UK airspace at present. We're just waiting to see which way the ash plume moves.

"We should have more of an idea within the next 12 hours or so."

'Larger particles'

A National Air Traffic Services (NATS) spokeswoman said: "We are not speculating at all at this stage, we are just watching the situation closely. It's changing all the time."

The Grimsvotn volcano, which lies beneath the ice of the uninhabited Vatnajokull glacier in southeast Iceland, began erupting on Saturday.

University of Iceland geophysicist Pall Einarsson said the eruption was on a different scale to the one in Iceland last year.

"It is not likely to be anything on the scale that was produced last year when the Eyjafjallajokull volcano erupted," he said.

"That was an unusual volcano, an unusual ash size distribution and unusual weather pattern, which all conspired together to make life difficult in Europe."

The ash particles from this eruption are said to be larger than last year, and as a result fall to the ground more quickly.

A Department for Transport spokeswoman said: "We are monitoring the activity in Iceland closely, together with the Met Office and NATS.

"We will be reviewing the situation regularly in case of any threat to European airspace."