Heavy snow brought much of London's transport to a halt today with airport runways forced to close and all bus and many train services suspended.

Heathrow, the world's busiest airport, said heavy snowfall overnight and more expected during the day meant "flights to and from the airport today will be subject to significant delays and cancellations".

An Air Malta flight due to have left for Heathrow just before 8 a.m. was still in Malta at 11.15 a.m.

Gatwick airport, the city's second largest, and Stansted, to the northeast, said they expected similar problems. An Air Malta, however, managed to operate a flight to Gatwick.

London City airport in the heart of the British capital said it was "closed until further notice".

Britain's Met Office said some parts of the country, including London and other parts of south East England, could be covered by up to 15 centimetres of snow by midday on Monday.

It issued a "severe weather" warnings for many parts of the south east of England, with weather experts saying the south east of the country was experiencing some of its worst snow since the early 1990s.

So far, this winter has been Britain's coldest in over a decade and forecasters expect the cold weather to continue for several more days.

Transport for London said all London buses -- which would normally carry 6 million people on an average day -- had been withdrawn from service "due to adverse weather and dangerous road conditions" and reported problems on all but three of the capital's eleven underground train lines.

Overground railways in south east of England were also badly affected, with some rail firms cancelling all train services in and out of London.