Firefighters backed by aircraft dropped water and foam on the birthplace of the ancient Olympics Sunday to stop wildfires from burning the 2,800-year-old ruins, one of the most revered sites of antiquity.
The fires continued to rage unabated as the national government declared a state of emergency.
New fires broke out faster than others could be brought under control.
Some villages were trapped within walls of flames, cut off from firefighters and, in some cases, from firefighting aircraft grounded because of high winds.
Desperate people called television and radio stations pleading for help that they feared would not arrive in time.
'I can hear the flames outside my door,' one caller from the village of Andritsena told a Greek television station, according to Reuters news service. 'There is no water anywhere. There is no help. We are alone.'
Although most of the fires have been on the Peloponnesian Peninsula, some broke out on the outskirts of Athens on Saturday, forcing the evacuation of homes and a monastery and closing a major road linking the capital to the main airport for several hours. The national fire brigade said that by evening it had brought those blazes under control, including one that came within about six miles of the city.
The country has been vulnerable to fire this summer because of drought and three consecutive heat waves that sent temperatures soaring over 100 degrees. More than 3,000 forest fires have razed thousands of acres of wooded areas since June; the earlier fires killed nine people.
The latest spate of fires on the peninsula started Friday. Strong, hot winds have spread the flames.
'The situation is unbelievable,' said Yiannis Stamoulis, a spokesman for the Greek Fire Brigade. 'We're dealing with savage forces of nature and it's humanly impossible to effectively take them on, however strong and well prepared we may be.'
He added, 'We're fighting an asymmetrical war.'
Firefighters expect the death toll to rise, because they have not yet been able to search some areas that had been overrun by flames.
Hardest hit by the fires were a dozen hamlets tucked into the rural highlands around the town of Zaharo in the western peninsula, where at least 12 people, including some who may have been trying to flee by car, were killed.
Charred bodies were found in cars, houses and fields in areas around Zaharo, firefighters said.
At least some of the people there were believed to have been killed or trapped after a collision between a fire truck and a convoy of cars apparently trying to flee the flames.
Scores of other residents, including elderly and disabled people, remained trapped in their homes, phoning in to local television and radio stations, crying for help.
'Help! Help! Help!' wailed one resident as he spoke with Mega television from the town of Artemida. 'Get some one here fast. We're losing everything.'
Minutes later, another caller pleaded for authorities to help save her two children, one of whom she feared was in shock after having seen their home go up in flames.
South of Zaharo, rescue teams confirmed at least six deaths in the seaside town of Areopolis, in the Mani region, a popular tourist destination known for its rugged cliffs and ravines.
Among the victims in the area were a pair of French hikers who were trapped in a flaming ravine. Their charred bodies were found locked in an embrace, the authorities said.
Hotels and dozens of surrounding villages have been evacuated.
The overstretched national fire services are being helped by an estimated 6,000 soldiers mobilized for the operation.
A fleet of water-dumping aircraft was expected from France, Germany and Norway, after Greece appealed to the European Union for 'urgent assistance.'
An Arizona study last year said rising temperatures and earlier melting of snowpacks had sharply increased the number of Western wildfires - the scientists involved expected more wildfires in the future.
Like hurricanes along the Eastern Seaboard in the US, forest fires have become a visible symbol for many in the West of the possible effects of climate change, Prof. Steven Running said. 'Only a hurricane is over in a day or two; these forest fires can last for months.'