The ministry's Forest Fire Prevention Agency said four of the nation's administrative districts would face a "maximum" risk of wildfires while the remaining 14 were also at "very high" risk, the second-highest alert level.

The four districts on maximum alert for wildfires -- Braganca, Castelo Branco, Porto and Vila Real -- are all in the centre and north of the country.

The national weather office forecasts temperatures will soar above 35 degrees Celsius (96 degrees Fahrenheit) on Wednesday across large parts of Portugal, which is facing its worst drought since the 1940s.

Wildfires have destroyed more than 38,000 hectares (94,000 acres) of forest and brush since the beginning of the year while six firefighters have died battling the flames.

Last month a 74-year-old man died and several mountain villages in central Portugal had to be evacuated before the arrival of light rain and cooler temperatures helped firefighters bring blazes under control.

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