The fire in the Sierra de la Culebra, a Spanish nature reserve, has caused the evacuation of 11 villages, it said Saturday, Xinhua reported.
Hundreds of firefighters and emergency personnel, as well as 40 fire engines, 20 helicopters and four aircraft, have been dispatched to fight the blaze, which was sparked by a lightning strike on Wednesday.
The fire still "had two fronts which are very active," Angel Manuel Sanchez, an official of Castile and Leon's fire brigade, told local TV network RTVE.
Spain has endured a week of an unusually early heatwave, as temperatures above 40 degrees Celsius were recorded in many cities and areas throughout the past few days. The heat is expected to begin to ease on Sunday.