LONDON (AFP) - Heavy snow disrupted European flights over the weekend and stranded hundreds of drivers as far south as Italy as a white Christmas appeared increasingly likely in many countries. On the final weekend for travellers before Christmas, some of the continent's biggest airports were shut, forcing thousands to bed down in the terminals and leaving some in no man's land, without a visa to leave the transit lounge. London Heathrow, the world's busiest international passenger airport, remained paralysed Sunday due to ice on the tarmac, with no flights coming in and only a handful leaving. Thousands were stuck there overnight, with furious pop singer Lily Allen among those caught up in the drama. The west London airport hopes for a "full re-opening on Monday". Hundreds more slept at London Gatwick, Europe's eighth busiest passenger airport. "Today is Gatwick's busiest day of the festive getaway and we are doing everything we can to get passengers on their way," a spokeswoman said. Eurostar, which runs high-speed passenger trains linking London with Paris and Brussels, was operating with speed restrictions that added up to an hour on journey times. Sporting events were also hit, with Sunday's big English Premier League clash between title rivals Chelsea and Manchester United postponed and European Cup rugby union matches called off. Temperatures plunged to minus 19 degrees Celsius (minus two degrees Fahrenheit) in Pershore, west central England. Britain's Met Office national weather service said snow falls this month have been the heaviest for December since 1981. airport, Germany's busiest, cancelled more than 540 flights Sunday due to heavy snow, with further flurries expected. A Frankfurt spokeswoman predicted more flights from the around 1,300 scheduled would be axed. More than 1,000 stranded passengers had to spend the night on beds set up in the airport terminals, some for a second night. Two runways at Paris's Roissy-Charles-de-Gaulle airport, continental Europe's biggest air hub, reopened Sunday but the other two were closed as fresh snow fell. Some 40 percent of flights were to be cancelled, aviation authorities said. Several hundred passengers whose planes were rerouted to Roissy due to the closure of London Heathrow on Saturday spent the night in departure lounges. The authorities asked other airports to stop diverting flights to Roissy until 2:30 pm (1330 GMT) to help ease the backlog. Some 20,000 passengers were patiently awaiting their flights at various Roissy terminals. Some 450 aircraft were however able to take off with delays averaging one hour and 20 minutes. Incoming flights were running an hour late. Orly airport, south of Paris, faced much less disruption with flights running 45 minutes late on average and several cancelled. Only a few bus services in the French capital were operating Sunday and none at all in the suburbs, a spokesman for the city transport authorities said. The city's iconic Eiffel Tower was closed to visitors. In the Netherlands, several hundred people spent the night at Amsterdam-Schiphol airport, where air traffic continued to be severely disrupted on Sunday. In northern Italy the situation was improving after two days of chaos on the roads and in the airports in Tuscany. Pisa airport, the hub of several budget airlines, reopened Sunday having been closed since Friday. Around 200 passengers forced to spend the night in the airport were issued with blankets and hot drinks. In Belgium, around 1,500 people spent the night at Brussels airport. Most of them were on 18 rerouted flights bound for Heathrow. Because Britain is outside the Schengen zone (passport-free travel within Europe), many passengers did not have the necessary visas to leave the transit lounge. In the Balkans, four people froze to death this weekend. Two men, aged 72 and 50, were found around Banja Luka in Bosnia, while an elderly couple were found dead by their neighbours in Serbia. In Croatia, temperatures plummeted to minus 21C (minus 5.8F) in the northern town of Cakovec. The snowfall even reached as far south as Algeria, where two people died in a road accident and traffic ground to a halt on several major roads. The snow that brought the chaos was moving slowly south over Europe, but the cold weather was expected to continue across much of the continent into next week.