Snowbound European airports raced Wednesday to clear a backlog of stranded passengers as better weather conditions allowed them to begin frantic efforts to get people home for Christmas.

In London, Paris and Frankfurt, the continent's busiest airports were running a slimmed-down schedule in a bid to get thousands of weary travellers to their destinations before Christmas Day on Saturday.

Airport officials were under increasing pressure to resolve the crisis after the European Union blasted the "unacceptable" disruption, with the head of Heathrow's operator BAA saying he would not take his yearly bonus.

Around 1,000 passengers spent the night at London Heathrow, the world's busiest international passenger airport, in the hope of flying out after days of cancelled flights and frustration.

"We're running 70 percent of our normal planned schedule, which accounts for around 900 flights," a Heathrow spokeswoman told AFP.

"The airport is fully operational and it's now a situation of airlines getting aircraft and crew in the right place," she said, adding that 30,000 tonnes of snow had been shifted from the airport's apron.

Heathrow was "absolutely" aiming to get everyone away in time for Christmas", the spokeswoman said, adding however that "we can't give any guarantees," she added.

British Airways said it had put on extra flights in a bid to fly "tens of thousands" of customers to their destinations before Christmas after having to cancel 2,000 flights during five days of "very severe" disruption.

It aimed to operate a full long-haul schedule on Thursday and Friday and said it hoped to run the "vast majority" of short-haul flights.

"Our teams are working around the clock to get as many people where they want to be ahead of Christmas Day and we are doing all we can to increase the number of seats available," chief executive Willie Walsh said.

Eurocontrol, the continent's air traffic supervisory body, said about 3,000 flights had been cancelled across Europe on Tuesday, with similar numbers of cancellations for each of the previous four days.

Weather reports said snow could persist in northern Europe even as the situation improved further south.

Colin Matthews, the head of Heathrow's operator BAA, said he would not take his bonus for 2010 after union chiefs said accepting the payment would be an "absolute slap in the face" to stranded passengers.

At Paris-Charles de Gaulle, continental Europe's busiest airport, 15 percent of flights were cancelled late Wednesday as snow flurries were forecast, while the schedule was to be slashed by 25 percent throughout Thursday.

An inter-ministerial crisis centre said that between five and 10 centimetres (two and four inches) of snow would fall, and authorities issued weather alerts for northern France.

Police authorities told Paris businesses to let their employees go home early and advised drivers to stay off the roads if possible.

Services at Frankfurt Airport, Germany's main hub, were improving though 70 early flights were cancelled. Overnight some 300 people slept in the terminals, while others were taken to local hotels.

"If the weather holds up, we will get a lot of passengers to their destinations today, but it also depends on the weather at other European airports," an airport spokesman told AFP.

German flag carrier Lufthansa said it expected a "quasi-normal situation" for flights on Wednesday.

Flights got going again at Dublin Airport after the authorities cleared ice and more than 15 centimetres (six inches) of snow, and also at Brussels Airport, with only a few flights to Switzerland scrapped.

Thick fog grounded planes at the Bulgarian capital Sofia, forcing diversions.

While rail services across Europe were also affected, Eurostar was able to run 43 out of 52 high-speed passenger services between London, Paris and Brussels after severe disruptions earlier in the week.

The wintry weather caused cancellations and delays on public transport across Scandinavia.

Denmark recorded its lowest December temperature since 1981, minus 22.5C (-8.5F).

In Russia, eight people were killed when a bus smashed into a truck in the western Siberian region of Krasnoyarsk.

The accident may have been due to a technical malfunction caused by temperatures dropping to minus 50 degrees Celsius (minus 58 degrees Fahrenheit).

Increased oil consumption in the cold weather pushed brent crude prices to new two-year highs in Asian trade, with a barrel rising 29 cents to 93.49 dollars.

Meanwhile, some 2,000 pagans, druids and revellers celebrated the winter solstice at the Stonehenge monument in southwest England by having a snowball fight at sunrise.