ATHENS, Greece — Wildfires intensified across southern Europe on Wednesday with a round-the-clock battle to protect the perimeter of Greece’s third-largest city and at least three deaths reported in Spain, Turkey and Albania.

Spain, Portugal, Turkey and the Balkans have also battled wildfires in recent days as a heatwave pushed temperatures over 40 C (104 F) across parts of Europe. In Albania and Montenegro, wildfires have destroyed houses and possessions since last week.

Thousands of firefighters are battling blazes as the continent continues to swelter in dangerously high temperatures.