The wildfire tearing through Belgium's High Fens nature reserve has become the largest ever recorded in the country, after burning through more than 27 square kilometres of land near the German border.

The fire broke out on Friday in Liege province and has continued spreading east since, according to Al Jazeera and Reuters reporting. It has now surpassed Belgium's previous record wildfire, a 2011 blaze that burned 14 square kilometres of the same reserve, according to the European Forest Fire Information System.

More than 250 emergency services personnel have been deployed to fight the flames, drawn from Belgium, Germany, Luxembourg and the Netherlands. A spokesperson for the government of Wallonia, Stephanie Ernoux, told Reuters that crews are focused on containing the advancing edge of the fire rather than the areas already burned.

Residents told to leave as smoke shifts

About 600 people in the Belgian border towns of Waimes and Butgenbach were told to evacuate on Saturday after winds shifted and pushed smoke toward their homes. Authorities said as of Sunday morning no homes had been damaged, though they continued to urge people to stay well away from the fire zone.

Just across the border, the German town of Monschau said the flames had come within about three kilometres of its territory. Officials there said they did not expect the fire to actually cross into Germany, but still advised residents in three of the town's districts to leave temporarily because of the smoke.

The fire followed a fresh burst of extreme heat in Belgium, with temperatures reaching around 37 degrees Celsius on Friday after weeks with almost no rain. Belgium is far from alone in this. Much of Europe has been through repeated heatwaves this summer, with several countries recording temperatures above 35 degrees on Thursday and parts of west London hitting the hottest day of the year at just over 38 degrees. Fires have followed close behind the heat, driving thousands from their homes in Germany, France, the United Kingdom, Croatia and Greece in recent days, with roughly 500,000 hectares burned across the European Union so far this year.