Fire crews in France and Spain battling unchecked wildfires that have forced more than 300,000 people to flee were overwhelmed on July 26 as the unpredictable blazes advanced.

Three firefighters were killed and 12,000 people were forced to evacuate as wildfires continued to ravage areas of southern France, Italy and Spain.

Thousands of residents and vacationers fled raging wildfires across France and Spain on Friday as fast-moving blazes, fueled by extreme heat, drought and...