ATHENS - Greek Prime Minister Kyriakos Mitsotakis said on Thursday evening that Greece is facing an extremely critical situation with multiple forest fires at the same time, while saving human lives is the government's top priority.

"The difficulties are still ahead of us. We have unprecedented conditions as we had ten days of extreme heatwave that turned the country into a powder keg," he said in an address broadcast live on public broadcaster ERT.

Firefighting forces are battling relentlessly to contain the fires that sprung up across the country.

Wildfires in the north of Athens leapt back to life on Thursday as Greece also faces flare-ups on the island of Evia, in Ancient Olympia in the northwestern Peloponnese and in other parts of the country.

Despite the efforts of the firefighters to contain the previous fire that burnt 1,250 hectares of forest and other land on Wednesday, the fire-stricken area of Varybobi in the north of Athens flared up on Thursday noon, with a new major fire front in the foothills of Parnitha Mount, leading to the evacuation of five settlements nearby.

At least four volunteers who were assisting in the fronts and one firefighter were transferred to hospitals, Greek national news agency AMNA reported.

The power supplier warned later of possible scheduled power interruptions in the Attica Region, depending on developments of the fire burning in the area.

Similar scenes were unfolding in the northwestern part of Evia island where the blaze continued to rage since Tuesday. More than 20 villages have been evacuated.

Earlier on Thursday, Mitsotakis visited the fire-stricken regions in Ilia prefecture, including Ancient Olympia, the birthplace of the ancient Olympics, where firefighters fought all night to save the well-known archaeological sites. The fire burning in the area for a second day has led to the evacuation of 32 communities.

"A total of 99 new flare-ups were recorded in Greece today, while authorities had to manage 145 fires in the last 24 hours," Deputy Minister for Civil Protection and Crisis Management Nikos Hardalias told a press briefing.

To back up the firefighting efforts, Greece deployed in the battle the armed forces with helicopters, aircraft, drones and soldiers.

Apart from Sweden and Cyprus, France, Romania and Switzerland also responded to the activation of EU's emergency mechanism for disasters, sending ground and aerial aid to help Greece put out the blazes.