MADRID (AFP) - Spain baked in a record-breaking heatwave on Thursday (July 13) which was blamed for the death of a road crew worker, and said to have left another man in critical condition.

The 54-year-old male victim died of suspected heatstroke late Wednesday while laying asphalt near the town of Moron de la Frontera in the south-western province of Seville, emergency services said.

Temperatures reached 43 deg C in Moron de la Frontera on Wednesday. Spain's largest union said it was investigating how long the man had been working and if the crew had taken special precautions because of the heat.

Meanwhile, a 50-year-old man is in critical condition in hospital after suffering heatstroke on Thursday while replacing pipes in Cabeza del Buey, a town in the south-western province of Badajoz, local media reported.

Spain's meteorological agency said seven cities including the capital Madrid set record temperatures for the month of July on Thursday.

It soared to 40.2 deg C in Madrid, smashing a previous record of 39.6 deg C recorded in 2015.

New record highs were also set in Badajoz, Caceres, Ciudad Real, Cordoba, Jaen and Teruel.

The heatwave - caused by a mass of hot air from northern Africa - will last until at least Sunday, officials say.