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.

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 roadways 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.

The main airports in Brussels and Charleroi were operating normally, with only some slight delays reported, the radio station said.