"The fires have approached the villages near ancient Olympia," Diamandis said. "We have launched evacuation operations."
One resident of a nearby village told a Greek television station: "We're going to burn alive here."
She said people were using garden hoses in an attempt to save their homes.
About 40 villages had been evacuated in the Peloponnese and on Euboea by early on Sunday.State of emergency
The Greek government has declared a state of emergency as more than 1,000 firefighters, backed by 425 soldiers and 16 water-dropping aircraft, battled the flames.
Nicole Itano, reporting from the capital Athens, said the announcement of a state of emergency was highly unusual in Greece.
"The state of emergency will give them more power to requisition private property and force evacuations," she said.
Most of the victims of the fire have been found in the Zacharo region, in the west of the peninsula, and include seven children, according to police.
Fires have also erupted on Evia, the second-largest Greek island, north of Athens, where several seaside resorts have been evacuated.
There were fears that the death toll would rise as emergency services searched devastated areas.
The government has said it suspects that many of the deadly fires were started deliberately.
On Saturday, a 65-year-old man was charged with arson and homicide in a fire that killed six people in Areopolis, a town in southern Greece, a fire department spokesman said.