They were called to the fire at about 3.20pm near Craig’s Forest, in the Finvoy area.
There are, at time of writing, six fire engines and another two specialist vehicles present on the scene.
In all, there are 48 firefighters at work.
Area commander Dermont Rooney told the News Letter that the firefront is about a kilometer long (about 0.6 miles), and he expects that an area the equivalent of around four or five football pitches could be burned.
Whilst gorse fires are not unusual at this time of the year, commander Rooney said this one is a “fairly significant incident” – and one which could continue for much of the evening.
Although the cause of the fire is under investigation, he said that the public at large should in general be wary about the risk of igniting dry scrub through discarding cigarettes, for instance.