Flights across much of Europe will be severely disrupted well into Saturday because of drifting ash ejected from a volcano in Iceland, officials said.

Much of the airspace across northern and western Europe has been closed and air control officials said some 17,000 flights would be cancelled on Friday.

Hundreds of thousands of passengers in Europe and around the world have been affected by the disruptions.

Scientists say the volcano is still erupting but producing less ash.

Europe's intergovernmental air control agency, Eurocontrol, said it "expects around 11,000 flights to take place today in European airspace. On a normal day, we would expect 28,000."

Of about 300 trans-Atlantic flights that would usually arrive in Europe in the morning, no more than 120 made it over, the agency said.

"Forecasts suggest that the cloud of volcanic ash is continuing to move east and south-east and that the impact will continue for at least the next 24 hours," it said in a statement.

'Dynamic situation'

More countries moved to close their airspace on Friday morning, joining eight which banned flights on Thursday.

Britain's air traffic control body extended its unprecedented restrictions on UK airspace until at least 0100BST on Saturday.

Exceptions allowed for Northern Ireland and western Scotland saw the first flight leave UK airspace since the ban was imposed, an Air Transat plane bound for Toronto from Glasgow.

"In general, the situation is dynamic and subject to change," said a statement issued by the National Air Traffic Service on Friday morning.

The UK, Irish Republic, Denmark, Norway, Sweden, Finland, Belgium and the Netherlands closed their airspace on Thursday.

France shut down 24 airports in the north of the country, including the main hub of Paris-Charles de Gaulle, while Germany's Berlin and Hamburg airports were also closed on Thursday evening. Frankfurt closed on Friday morning.

Poland closed most of its airspace on Friday but kept Krakow and Rzeszow airports in the south open. Austrian officials said they would have to start closing their country's airspace from late afternoon.

Czech authorities began to impose restrictions on Friday as well, adding that a complete closure was likely to follow.

But as the volcanic ash began drifting south, Sweden began reopening its northern airspace. Officials said restrictions further south would be lifted gradually on Friday. Norway allowed some flights in the north as well.

The Irish Republic also opened its airspace apart from a block off the south coast, putting Dublin, Shannon and Cork airports back into operation.

Qantas, Japan Airlines, Korean Air, Singapore Airlines and Cathay Pacific were among airlines who have cancelled long-haul flights to Europe.

Qantas spokesman David Epstein said it may take until Sunday for flights to resume.

Eurostar said its train services between London and Paris and Brussels was sold out on Friday and urged people not to come to St Pancras station in London to look for tickets.

If the disruption persists, there are fears in Poland that some world leaders will be unable to attend Sunday's state funeral of Polish President Lech Kaczynski, who was killed in a plane crash last Saturday.

Several European monarchs were unable to attend 70th birthday celebrations for Denmark's Queen Margrethe, which began with a concert on Thursday.

Ash subsiding

The volcano began erupting on Wednesday for the second time in a month, hurling a plume of ash 11km (seven miles) into the atmosphere. A 500m-wide fissure appeared at the top of the crater.

The heat melted the surrounding ice, and witnesses said two flows of meltwater started coming off the glacier on Wednesday.

As many as 800 people were evacuated from their homes as water carried pieces of ice reportedly the size of small houses down the mountain. A road along the flooded Markarfljot river was also cut in several places.

On Thursday, the flooding was reported to have subsided.

Matthew Roberts, from the Icelandic Met Office, told the BBC the eruption was weakening and it was no longer producing as much ash.

British health officials said the effects of the ash on people with existing respiratory conditions were "likely to be short term".

Particles that fell overnight Thursday on the Shetland Isles were being examined by the Scottish Environment Protection Agency.

The last volcanic eruption beneath the glacier was on 20 March. The eruption before that started in 1821 - and continued for two years.

Iceland lies on the Mid-Atlantic Ridge, the highly volatile boundary between the Eurasian and North American continental plates.