LONDON -- Civil aviation officials on Sunday said a drifting, dense cloud of volcanic ash is "rapidly encroaching" on British airspace, forcing the closure of airports in Northern Ireland.
The National Air Traffic Service said a no-fly zone has been imposed over parts of Northern Ireland, and no flights are going in or out of airports in Belfast or the Isle of Man.
Dublin and Shannon airports in the Republic of Ireland will stay open until 1 p.m..
Britain's Department of Transportation has warned that different parts of the country's airspace -- including England's southeast, home to Europe's busiest airport at Heathrow -- could close at different times through the next few days because of the eruption of Iceland's Eyjafjallajokul volcano.
Meanwhile, German air traffic control said its air traffic won't be affected by a possible return of the volcanic ash cloud before Wednesday.
In a statement issued late Saturday it said the latest weather forecast shows that the ash concentration will remain insignificant throughout Tuesday.
Air traffic controllers previously warned of the ash cloud's possible return for Monday, which could have led to the closure of German airports.
The German Aerospace Center and Lufthansa both announced test flights for Sunday to measure the ash concentration.