An ash cloud from Iceland briefly forced the closure of several north German airports on Wednesday, including Hamburg and Berlin, even as the Grimsvoetn volcano appeared to stop erupting.

The cloud is the second from an Icelandic volcano in barely a year to disrupt European air traffic and air traffic controllers said some 450 flights were cancelled over Germany on Wednesday.

The Brussels-based Eurocontrol had expected more flight cancellations earlier on Wednesday, when it had predicted that 700 flights would be grounded.

Airports in northern Germany, including those of Hamburg, Bremen, Sylt, Rostock and Berlin, were all closed for several hours Wednesday as the cloud moved south after crossing the North Sea.

But German Transport Minister Peter Ramsauer later announced that the cloud was "moving to the northeast", adding that "airports will reopen sooner than expected."

Meanwhile, in good news for travellers, geologists in Iceland said that activity at the Grimsvoetn volcano appeared to be over, at least for now, and the ash plume had almost disappeared.

"There has been no activity since about 0200 GMT this morning," Sigthrudur Armannsdottir of the Icelandic Meteorological Office said Wednesday, while adding that "it's too soon to say the eruption is (completely) over."

The volcano, the most active in Iceland, begun erupting on Saturday, sending a plume of smoke and ash 20 kilometres (12 miles) into the sky.

The worst of the eruption is over and authorities can now focus on cleaning up the areas covered in ash, Iceland's Prime Minister Johanna Sigurdardottir said Wednesday.

"The worst is over, and now the clean-up can begin," Sigurdardottir said in a statement.

"Problems arising in our neighbouring countries as a result of volcanic ash should be resolved quickly," he added.

Air traffic disruption in Germany did not affect major hubs in Frankfurt and Munich on Wednesday.

Lufthansa, the country's largest air carrier, said earlier that it expected to cancel some 150 flights from cities in the cloud's path.

Air safety officials had ordered several northern German airports closed in the early morning, but all had reopened by Wednesday afternoon.

On Tuesday, some 500 flights were grounded across northern England, Scotland and Northern Ireland as the cloud drifted by, but British airspace was reported clear Wednesday morning.

In The Netherlands, disruption was minimal Wednesday.

Passengers at Amsterdam's Schiphol airport "may see some flights to Germany -- Hamburg, Hannover, Bremen and now Berlin being disrupted, but otherwise operations continue as normal," Dutch air traffic control spokeswoman Marjolein Wenting told AFP.

The cloud was not expected to directly affect Dutch airports on Wednesday or Thursday, she added.

Further east, Denmark, which Tuesday had closed a small area of its airspace because of the cloud, said the situation had since returned to normal.

"The latest readings have shown there is no longer a concentration of ash in Danish airspace, allowing us to fully reopen it", Camilla Hegnsborg, a spokeswoman for air traffic control Naviair told AFP.

Airspace over parts of the North Sea remained closed, however, while Denmark, which is responsible for Greenland's airspace, said it had also ordered the closing of several areas surrounding it.

In France, civil aviation chief Patrick Gandil on Wednesday said French airspace would not be closed.

"All our airports will remain open," he said, adding that the G8 summit which was due to start Thursday in the northern seaside resort of Deauville "will not be impacted".

Many airlines, which suffered financially from last year's shutdown, say authorities are exaggerating the danger posed by the cloud.

Just over a year ago, ash spewing from another volcano, Eyjafjoell, caused the biggest aerial shutdown in Europe since World War II, affecting more than 100,000 flights and eight million passengers.