Around four to 10 centimetres (1.5 to four inches) of snow blanketed the kingdom, with more expected later Monday, raising the danger of treacherous black ice forming on roads as temperatures remained below zero degrees Celcius.

Transatlantic flights were delayed by up to three hours at the main Brussels airport, while most others were held up 10 to 20 minutes while de-icing was carried out, a spokesman said.

Four flights bound for Charleroi airport, some 40 kilometres (25 miles) south of the Belgian capital, were diverted to northern France. Two others were cancelled, said the airport, a low-cost hub, on its Internet website.

On the roads and railways in Brussels, public transport ran normally in the morning, apart from the derailment of one tram, while vehicles crawled into the capital amid light snowfalls.

Secondary arteries in some parts of the south of the country -- particularly the Ardennes region in Wallonia -- were virtually cut off, private Bel RTL radio said.

Buses were held up in Liege, to the east.

Power cuts were also reported.