Heavy snow shut Charles de Gaulle-Roissy airport, paralysed the Paris bus network and forced the operators of the Eiffel Tower to close the landmark tourist attraction on Wednesday, officials said.

Motorists were warned that all motorways in the Paris region had become impassable and truckers were ordered to pull off the highways and wait until conditions improved.

Roissy airport was to remain shut until at least 1600 GMT while workers tried to clear the runways of the heavy snow that began falling around midday, airport officials said.

One in five flights at Roissy had already been cancelled at the request of France's civil aviation authority (DGAC) due to the poor weather forecast.

The runways at Orly airport were earlier shut for about half an hour to allow workers to clear snow but there was no immediate information available on how flights at Paris' second airport were affected.

Only a handful of the 350 Paris bus routes were operating because of the snowfall in the capital, which had previously escaped the heavy snow affecting much of France since the start of the month.

The metro and overland suburban rail network were functioning normally.

The operators of the Eiffel Tower said they had already shut the first floor of the giant monument that is one of the world's most visited sites.

"But since late morning the Eiffel Tower has been completely closed and will certainly not reopen today," said a spokesman.

Salt cannot be used to fight snow or ice at the 324-metre (1,063-feet) tower because it would damage the iron structure that at this time of year gets around 12,000 visitors a day.

An early cold snap has caused severe transport disruption across Europe over the past week.