The Portuguese Institute of Sea and Atmosphere (IPMA) extended its red-alert warning into Sunday for 11 districts on Friday, due to record high temperatures in Portugal.

Lisbon is expected to peak at 41 degrees celsius, with nearby Santarem, Setubal and Evora forecast to register 43 degrees.

Beja, which will host the latest stage of the Tour of Portugal cycling race, will see thermometers pass the 40 degree mark.

Several towns witnessed their highest-ever temperatures on Thursday, with Coruche, a town 60 km northeast of Lisbon, tipping the scales at 44.9 degrees celsius.

With temperatures set to gradually rise into Sunday, Portugal's highest ever temperature, 47.3 degrees Celsius recorded in Amareleja, 175 km south of Lisbon, in August 2003, could be surpassed on Saturday.

The IPMA's red-alert is its most severe warning level. It cautions against elevated risks to public health and dangers of wildfires.

The National Civil Protection Authority (ANPC) has put six districts of Porto, Leiria, Aveiro, Braga, Viana do Castelo and Coimbra on maximum fire alert.

The army and navy have been called in to provide extra fire prevention and fighting support to the ANPC and fire services.