Known as procession caterpillars for the way they advance in straight lines through forests, the insects not only consume entire oak stands in their path but are covered in poisonous hairs that induce allergic reactions in people that include rashes and respiratory problems.
"The caterpillars are already 'at the gates' of Brussels," the radio said. "City authorities are taking preventive measures to turn back the insect hordes."
In the town of Leuven, 25 kilometers from the Belgian capital, more than 100 formations of the crawling things have been spotted, and a platoon of Belgian soldiers armed with blowtorches has been dispatched to the country's forests in an attempt to halt their advance by burning them off trees.
Brussels suffered a similar invasion four years ago, and residents have been asked by city authorities to be vigilant and report any sightings in parks and gardens.
So far, some 20 communes in the northern Flemish Brabant region have been overrun, and residents of several towns in Limburg, the easternmost province of Flanders, with a population of some 800,000, have been suffering from the pests for the last two weeks.
The caterpillars, which metamorphose into moths, are common in central and southern Europe, but have been moving northward in recent years, possibly as the result of a warming climate.
