Prime Minister Pedro Sanchez held a "coordinating crisis meeting" on Saturday to strengthen efforts against the fires in Castile and León, Galicia, Asturias and Extremadura.
At the same time, air support arrived from France and Italy, with planes landing at a base near the city of Salamanca. Spain and also Portugal, which is also affected by severe fires, have jointly appealed for support from the EU.
A dozen important roads have been closed and train traffic between Madrid and Galicia was stopped.
Around 3,500 soldiers have been deployed in the affected areas to participate in the extinguishing work, but voices are being raised for further reinforcement.
Smoke from the fires reaches as far as the United Kingdom, reported the British weather authority Met Office.
