Weather conditions slowly improving in Sweden - but travel authority urges travellers to leave their cars at home.

Thousands of travellers were stranded at Paris' main airport Friday as freezing conditions forced the cancellation of hundreds of flights, with many passengers facing delays into Christmas Day.

In Sweden, after a day in which thousands were stranded and delayed for hours due to train cancellations, the travel situation is slowing improving as trains are moving in most parts of the country, according to the Swedish Transport Administration. However, the authority has issued a warning to travellers to leave their cars at home.

“I know this is strange advice to give on Christmas Eve but unless you absolutely have to, you should not get into a car – particularly in Skåne but also in Blekinge, Kalmar County and Öland,” Transport Administration, spokesperson, Rebecka Starco, told news agency TT.

At least 400 flights in and out of Paris' main hub Roissy-Charles de Gaulle were cancelled, with flights in Belgium and Germany also affected and motorists staying off the roads as western Europe battled the latest cold snap.

"Of the 1,160 flights initially planned for during the day today, 200 departures and 200 arrivals have been cancelled," a spokesman for France's civil aviation authority DGAC told AFP.

One flight represents an average of 150 passengers, so the cancellations, largely due to problems de-icing aircraft, will affect around 60,000 people.

Junior transport minister Thierry Mariani said that airports were struggling to deal with the third bout of ice this month, with problems compounded by workers at France's main anti-freeze factory at Fos-sur-Mer being on strike.

A cargo plane carrying glycol from the United States arrived at Charles de Gaulle early Friday, an airport source said, with trucks bringing more anti-freeze from Germany due to arrive later in the day.

While rail operator SNCF said all Christmas trains would be running, around 40 passengers spent the night on a train stuck in the snow in the northern Somme region, with the Red Cross supplying them with blankets and hot drinks.

Many northern provincial roads were impassable by car, authorities said, and people were advised to stay at home.

Transport Minister Nathalie Kosciusko-Morizet warned that the flight delays could extend into Christmas Day for up to half of passengers at Charles de Gaulle.

Of those unable to travel, some local people returned home, others were put up on nearby hotels and two gym halls were opened by local authorities.

At the airport, officials set up hundreds of camp beds for passengers with nowhere else to go.

"It's unacceptable!" protested Zakaria Talhaoui, 29, who had been due to fly to Casablanca, Morocco, for his brother's wedding.

"Everyone's blaming each other, the company, the airport management," said his tearful wife, Malika.

"They've been giving us the runaround all day in the airport without taking into account the fact that I'm pregnant," she added.

Between 10 and 20 centimetres (four and eight inches) of snow fell overnight in Belgium, sowing chaos on the roads, with many buses and taxis in the capital Brussels unable to drive on snow-blocked streets.

Belgian trains were hit with severe delays as many railway employees were unable to make it to work, operator Infrabel said.

The motorway from Belgium to Luxembourg was cut by snow, and bus services in most cities in the hilly south of the country were not running.

Hundreds of plane passengers at Charleroi spent the night at the airport or in the hotel after their flights were cancelled.

In Germany, the country's third largest airport in Duesseldorf was shut down early Friday, a spokeswoman for the flag carrier Lufthansa told AFP.

"Duesseldorf is closed this morning, but it should reopen this afternoon," Bettina Rittberger said.

On the roads, one person was killed and 10 injured in a massive pile-up involving 51 cars on the A9 motorway between Berlin and Munich, media reports said.

More snow was expected across Germany during the day, and several trains ground to a halt overnight as service was cut between Hannover and Berlin, the national railway Deutsche Bahn said.

Hundreds of tourists on the Danish island of Bornholm were forced to spend the night in an army barracks or on the ferry after heavy snow overnight.

"Bornholm police ask people not to move around. Heading off on foot outside built-up areas is deadly dangerous and we ask people to stay at home," they said in a statement.

In Finland, temperatures plummeted to minus 30 degrees Celsius (minus 22 Fahrenheit) in much of the country overnight, including the capital Helsinki.

In Britain, where heavy snow last week caused widespread transport chaos, meteorologists warned of further snow and widespread icy roads in northeast England and eastern Scotland.

The Met Office forecast that temperatures would plunge to as low as minus 14 Celsius overnight Friday in central Scotland.

Train services were disrupted across large parts of the country, hitting travellers heading home for Christmas, although Heathrow airport was largely back to normal after the chaos of recent days.

In Ireland, Dublin airport reopened Friday after being closed for much of Thursday, stranding about 40,000 passengers.

Snow and ice crews worked overnight to clear about 120,000 tonnes of snow from the runway, a statement from the airport said.