Iceland's Eyjafjoell volcano is spewing more and more ash, prompting authorities to consider re-routing transatlantic flights and to warn more disruptions are possible.

"Ash production did increase last night and the ash plume is going higher now than the last couple of days," Agust Gunnar Gylfason, who monitors the eruption's progress at Iceland's Civil Protection Department, said.

European airspace and airports across the continent were open yesterday, but intergovernmental air traffic control agency Eurocontrol said the ash cloud could mean transatlantic flights might need to be re-routed.

"Significant re-routing of westbound transatlantic flights to avoid the higher contaminated area is currently being discussed between the air navigation service providers concerned and Eurocontrol," the Brussels-based body added.

The area where concentrations of ash could still pose a risk to aircraft engines was lying to the north and west of Ireland, it said.

Airspace above Ireland, Northern Ireland and Scotland was partly shut on Tuesday and Wednesday, causing the cancellation of hundreds of flights, after winds had blown ash clouds down from Iceland.

The fresh disruption came after Europe's skies were closed for up to a week last month by the eruption of the Eyjafjoell volcano. It was the biggest aerial shutdown in Europe since World War II, with more than 100,000 flights cancelled and eight million passengers affected.