Greek fire crews on Thursday scrambled to douse deadly wildfires raging for two weeks around the country before strong winds forecast for the day rekindled blazes.

Hundreds of firefighters backed by European Union reinforcements were struggling to contain the flames on the islands of Rhodes, Corfu and Evia, in addition to a new front that erupted Wednesday in central Greece.

"These are difficult and very sad days," Prime Minister Kyriakos Mitsotakis said.

Mitsotakis said Greece was "mourning four fellow citizens, the two aircraft pilots... and two who could not distance themselves from the inferno in time."

Five bodies have been recovered from fire-stricken areas this week, but a police source told AFP that a cattle farmer found burned on the island of Evia on Tuesday had disappeared before the fire and was not listed among the wildfire casualties.

Around the Mediterranean, fires this week also flared in Croatia and Italy, and flames killed 34 in Algeria in extreme heat that has left landscapes tinder dry.

- Mass evacuations -

Officials have said more than 600 wildfires have broken out around Greece since July 13, with the vast majority tackled before becoming a threat.

The civil protection ministry warned of extreme danger of fire in over a dozen Greek regions Thursday.

A forest fire broke out Wednesday in mountainous terrain near the Greek-Bulgarian border, and was still out of control.

Early Thursday, another fire broke out near homes in the leafy Athens suburb of Kifissia, but was swiftly extinguished.

In a town near the port city of Volos in central Greece, evacuations were ordered after fires burning since Wednesday caused an explosion in an ammunition warehouse.

"Part of the ammunition warehouse at the air force barracks in Nea Anchialos is on fire and an explosion has taken place," said fire service spokesman Yannis Artopios, adding that seven planes and three helicopters were on site to put out the blaze.

Tens of thousands of residents and tourists at the height of the busy travel season have been evacuated, including 20,000 people on Rhodes, where officials declared a state of emergency this week.

On Tuesday, two pilots died when their water-bombing plane crashed while battling a blaze in Evia.

A dangerous fire broke out Wednesday near the industrial zone of Volos, leaving two dead.

An elderly disabled woman was found dead inside her burned camper van in a coastal area near Volos, and a cattle farmer was killed while trying to rescue his livestock.

The industrial zone was closed Thursday as a precaution. Six communities and villages around the city of nearly 140,000 people were evacuated early in the morning, with more placed on standby.

Temperatures are expected to drop Thursday after a prolonged heatwave but near-gale winds are expected to complicate efforts to douse the fires.

In some cases, locals have ignored evacuation orders and stayed behind to help save their homes and bolster the badly-stretched firefighting crews.

"We have a better knowledge of the local roads and surrounding area, we can make a contribution," Manolis Seitis, a 19-year-old student, told AFP at the village of Vati in Rhodes.

"We organise ourselves," added Nektaria Kabouri, a 33-year-old mathematician helping to distribute water and snacks to exhausted firefighters.

"People from surrounding villages immediately came to help... these forests belong to all and we want to protect them."

- Compensation -

"Very high temperatures of over 40 degrees Celsius (104 Fahrenheit) and intense winds have created fire fronts of many kilometres," Civil Protection Minister Kikilias said, adding that crews were battling through "inconceivable fatigue."

In Italy, three people died as a result of the fires earlier this week, with investigations underway into a potential fourth victim, after a 61-year-old woman was found dead in a lift stuck for several hours in Palermo, potentially because of an electricity blackout.

Sicily's civil protection agency estimates fires that have swept the island in the last two days "have caused more than 60 million euros in damage".

Prime Minister Giorgia Meloni's government Wednesday approved 10 million euros to compensate tourists whose trips to Sicily have been disrupted by the fall-out from the heatwave.

This includes those affected by the closure of Catania airport, hit by fire on July 16 and offering only a vastly reduced service since then.

Catania and surrounding areas have also suffered blackouts and water shortages in the past week that electricity suppliers blamed on heat damage to underground cables.