Iceland's Eyjafjoell volcano spewed more ash on Tuesday than in recent days, but the level remained much lower than when the eruption began three weeks ago, an Icelandic geophysicist told AFP.
"The plume has increased. It is black ... There is more ash in the plume and it is (rising) higher," Sigrun Hreinsdottir of the University of Iceland in Reykjavik said on Wednesday.
Ireland reimposed a partial ban on flights early Wednesday as the cloud of volcanic ash drifted south from Iceland, while flight restrictions were also imposed in Scotland and Northern Ireland.
"There was more activity yesterday (Tuesday) than during the past days, but much less than during the first days of the eruption," Hreinsdottir said.
She added that the ash and steam plume on Tuesday reached 20,000 feet, or 6,000 metres.
On Monday, experts said the plume reached as high as 5,200 metres, far lower than its peak of around 9,000 metres at the pinnacle of the chaos.
Scientists have stressed the height of the plume is not necessarily a reflection of the quantity of emitted ash.
Iceland's Eyjafjoell volcano began erupting on April 14, sending a cloud of ash into European skies that paralysed airspace for a week.