(AFP) - The death toll from the vicious cold snap across Europe has risen to more than 260, with the winter misery set to hit thousands of those seeking to escape it Sunday as air traffic was hit.

Ukraine has suffered the heaviest toll with 122 deaths, including many who froze to death in the streets as temperatures plunged to as low as minus 38.1 degrees Celsius.

Airports were shut, flights and trains delayed, and highways gridlocked as emergency services raced to clear falling snow.

London's Heathrow Airport, Europe's busiest air passenger hub, cancelled 30 per cent of its flights Sunday to cope with heavy snowfall overnight and possible freezing fog.

Heathrow said up to 10 centimetres of snow were expected to fall which, without reductions to the flight schedule, would cause major disruption at the west London airport.

"We deeply regret any disruption caused to passengers by the cold weather," said Heathrow's chief operating officer Normand Boivin.

"Reducing the flight schedule means we can fly as many people as possible and return the airport to normal as quickly as possible."

The changes could affect around 400 flights at the world's busiest airport for international passengers.

In the Netherlands, Amsterdam-Schiphol airport reported dozens of delays and cancellations on Saturday.

In Italy, the poor weather also hit boat passengers, when the ferry Sharden hit a breakwater shortly after setting off from the port of Civitavecchia near Rome on Saturday.

It caused panic among the 262 passengers who feared a repeat of a cruise ship tragedy in the area last month that is thought to have killed 32 people.

Coast guard spokesman Carnine Albano said the accident, which tore a 25-metre hole in the ship's side above the waterline, happened after the vessel was buffeted by a violent snow storm from the north-east.

All passengers were evacuated and no injuries reported.

The heaviest snowfall in 27 years here, better known for its warm sunshine, to grind to a halt with taxis and buses unable to navigate through the icy streets without snow chains.

Parts of the Venice lagoon also froze over.

Among the cold-weather deaths in Italy was 46-year-old woman who died in Avellino, near Naples in southern Italy, after a greenhouse roof laden with snow collapsed on her.

A homeless man in his sixties of German origin was found dead, apparently of cold, in the central town of Castiglione del Lago. These latest deaths brought the total in Italy to seven.

In Poland, the death toll rose to 45 as temperatures reached minus 27C in the north-east. In Romania, four more victims were found, bringing the number of fatalities in the country to 28.

The cold snap has also killed people in Bosnia, Latvia, Lithuania, Estonia, Bulgaria, the Czech Republic, Italy, Slovakia, France, Austria and Greece.

In France, snow fell from Lille in the north to Marseille in the south, though the west of the country and the capital Paris were spared.

A 12-year-old boy died in the eastern city of Strasbourg when the ice broke as he played with a friend on a frozen pond, paramedics said.

His friend, 11, was in hospital being treated for hypothermia after plunging in to try to save him.

Snow fell in Bosnia for the second straight day, paralysing traffic, with one patient dying as an ambulance was unable to reach his village in the south of the country.

In Serbia, a man was found dead in the southern town Lebane as the authorities in 28 municipalities, mostly in remote mountainous regions in the south and southwest, declared a state of emergency.

In tiny Montenegro, where one person was found frozen to death in a village, many hamlets in the mountainous north were cut off. Rescuers managed to evacuate 120 people, among them 31 school children from neighbouring Albania on a field trip, Interior Minister Ivan Brajovic said.

But as Europe huddled indoors for warmth, Russian gas giant Gazprom said it could not satisfy western Europe's demand for more energy.

"Gazprom at the moment cannot satisfy the additional volumes that our Western European partners are requesting," the company's deputy chairman Alexander Kruglov said at a meeting with Prime Minister Vladimir Putin, according to Russian news agencies.

Frigid temperatures even edged into north Africa, with the temperature forecast to drop below freezing in Algiers on Saturday night.

In Algeria's eastern region, a 17-year-old man was assumed killed after he was swept away by a swollen river. Many domestic and international flights were cancelled.