Media playback is unsupported on your device Media caption Grimsvotn volcano began erupting on Saturday

Airlines have cancelled flights and travel disruption is expected as a cloud of volcanic ash approaches NI.

Analysts expect the ash cloud from the Grimsvotn volcano in Iceland to reach Northern Ireland and Scotland by early on Tuesday.

The event comes a year after ash from the Eyjafjallajokull volcano spread across Europe, causing huge disruption.

Two flights between Belfast City and Dundee scheduled for Tuesday have been cancelled.

Belfast International, George Best Belfast City and City of Derry airports have urged passengers to check with their airlines for updates on flights.

The threat of air travel disruption led US President Barack Obama to fly to London ahead of schedule.

Mr Obama had been due to arrive for his state visit to the UK on Tuesday, after visiting the Republic of Ireland.

But White House deputy press secretary Josh Earnest said: "Due to a recent change in the trajectory in the plume of volcanic ash, Air Force One will depart Ireland for London tonight. The schedule for tomorrow will proceed as planned."

At least 36 Loganair flights in Scotland have been cancelled as the Civil Aviation Authority (CAA) warns that disruption cannot be ruled out.

Andrew Haines, chief executive of the CAA, said: "Our number one priority is to ensure the safety of people both onboard aircraft and on the ground.

"We can't rule out disruption, but the new arrangements that have been put in place since last year's ash cloud mean the aviation sector is better prepared and will help to reduce any disruption in the event that volcanic ash affects UK airspace."

The Met Office, which runs Europe's Volcanic Ash Advisory Centre, earlier said there was a possibility of ash moving across the UK towards the end of the week.

But a spokesman said the weather was much more changeable than at the time of last year's eruption and there was a lot more uncertainty.

The CAA said ash levels would be graded as low, medium or high, and airlines would be notified if levels reached medium or high.

Airlines would then consider whether to fly, according to risk assessments already carried out, the CAA added.

Foreign Secretary William Hague, speaking before a meeting of EU counterparts in Brussels, said he did not expect a blanket closure of UK airspace.

"I think we are far better prepared and we'll have far better information and intelligence which allows us to adjust things without necessarily the blanket bans on flights which we saw last year, but of course it depends on how the situation develops," he said.

The Foreign Office advised passengers to remain in regular contact with their travel agent or airline for the latest news on the status of flights and bookings and said British airports were currently not affected.