Reuters reported that more than 400 firefighters, backed by water launchers and 123 vehicles, were brought in after a fire broke out in a mountainous area of Mafra municipality.
A huge cloud of black smoke rose over the town of Venda do Pinheiro, in Mafra, as the fire forced authorities to close several roads and evacuate a nursing home.
Many locals left their homes in fear.
Smoke from the fire can be seen from downtown Lisbon, about 33 km to the south.
Other fires broke out elsewhere in Portugal, including in the central municipality of Ourem, where fires destroyed thousands of hectares two weeks ago.
More than 1,000 firefighters were mobilized across the country.
Like other European countries, Portugal has experienced a severe heat wave in recent weeks, with temperatures exceeding 40°C (104°F) in various parts of the country.
Although the heat has subsided, temperatures are rising again.
The meteorological agency IPMA said three regions in northern Portugal would be on “high alert” from extreme temperatures.
ZHB