The fire broke out late on Sunday evening in Parada, Arcos de Valdevez.
The alarm was raised at 18:30 in the bush area. More than ninety militants are involved in the battle, supported by 24 vehicles.
Before nightfall, aircraft also took part in the battle. There is no threat to houses, but the EN 303 road from Rio Frio to Monte do Castelo is closed to traffic.
After about 150 firefighters fought two fires in the same municipality on Saturday, about a hundred firefighters were mobilized again late Sunday.
The difficult-to-extinguish fire is now under control.
On Saturday, Arcos de Valdevez Fire Chief Filipe Guimarães said in a statement to Morning mailleft a call for people to cut down forests to avoid fires that have become constant in recent days in the municipality of Alto Minho.