More than 30,000 personnel, including firefighters from across the United States and nearly 140 from Australia and New Zealand, are battling the blazes.
The fire, which was 5% contained, was being fuelled by dry brush covering steep terrain and stoked by erratic wind gusts during the night.
Wildfires blazed along a smouldering stretch of Portugal's Algarve Thursday, as hundreds of firefighters battled to control flames that have menaced the popular tourist region for a week.
The Greek government, widely criticised for its handling of the devastating fires east of Athens which killed 90 people, on Sunday replaced its heads of the police and fire brigade.
Greece's minister responsible for the police, Nikos Toskas, quit on Friday after scores died in wildfires near Athens last month, Prime Minister Alexis Tsipras' office said.
The current death toll of 91 was expected to rise after the coastguard said another body was found underwater near a beach in the affected area.
Scores of locals and holidaymakers fled to the sea to try to escape the flames as they tore through towns near Athens.
Firefighters are gaining momentum as they battle several wildfires that have destroyed dozens of homes and forced the evacuation of thousands of residents in California.
The search for victims of last week's deadly mudslides in southern California continued on Monday, with hundreds of rescue workers with dogs and scanners hunting for four people still listed as missing.
Firefighters trying to tame a blaze that has destroyed hundreds of homes in Southern California were facing bone-dry conditions and the return of powerful wind gusts on Wednesday.
Brutal winds that fueled southern California's firestorm finally began to ease Saturday, giving residents and firefighters hope for respite as the destructive toll of multiple blazes came into focus.