Wildfires sweeping through a Greek resort town near Athens have killed at least 74 people, including families found clasped in a last embrace as they tried to flee the flames.

Dozens of the victims, including children, were found huddled together in a compound, while a some bodies were recovered from the sea where they had fled to escape the flames and smoke.

Prime Minister Alexis Tsipras declared three days of national mourning in response to the growing disaster amid fears the death toll could rise further.

As of Tuesday morning (AEST) authorities had no definitive figures on the number of people still missing in the fires.

Greek Interior Minister Panos Skourletis described the fires as a “national tragedy” and a “biblical disaster with human losses,” in an interview with Sky News.

As well as the dead, at least 164 adults and 23 children have been iinjured, the Associated Press reported.

Of the adults, 71 remained hospitalised, with 10 of them in serious condition, while 11 of the children were still in hospital.

Although the fires had largely abated by Wednesday morning, they were far from out.

Hundreds of firefighters aided by water-dropping aircraft were tackling the remaining areas in the two main blazes near the capital.

One blaze was northeast of Athens near Rafina, where most of the casualties appeared to have occurred, while the other was about 50 kilometres west of the city, where some flare-ups were reported Wednesday morning.

“Greece is going through an unspeakable tragedy,” Mr Tsipras said in a national televised address.

Emergency crews found the bodies of 26 victims, some of them youngsters, lying close together near the top of a cliff overlooking a beach.

They had ended up there after apparently searching for an escape route.
“Instinctively, seeing the end nearing, they embraced,” Nikos Economopoulos, head of Greece’s Red Cross, told Skai TV.

No Australians are believed to be among the dead.

“The Australian Embassy in Athens has confirmed with local authorities that no Australians are known to be affected by forest fires near Athens at this time,” a spokesperson for DFAT said. “The Embassy continues to monitor the situation closely.”

Many hours after the blaze broke out, the strong smell of charred buildings and trees lingered in the air in parts of Mati on Tuesday. White smoke rose from smouldering fires.

Residents, their faces blackened by smoke, wandered the streets, some searching for their burned-out cars, others for their pets.

Authorities are still unsure how many people are still missing. Photo: Getty

The eerie silence was punctured by fire-fighting helicopters and the chatter of rescue crews.

Many in the area were unable to escape the fast pace of the blaze even though they were a few metres from the Aegean Sea or in their homes, the fire service said.

“We went into the sea because the flames were chasing us all the way to the water. It burned our backs and we dove into the water,” fire survicor Kostas Laganos said.

He compared the ordeal to the destruction of the city of Pompeii, where thousands were incinerated by the volcano of Mount Vesuvius in 79 AD: “I said my God, we must run to save ourselves and nothing else.”

Many survivors fled to the beach for safety. Photo: AAP

Working through the night, coastguard vessels and other boats rescued almost 700 people who had managed to get to the shoreline and pulled another 19 survivors and six dead bodies from the sea, the coastguard said.

Boats combed beaches for any remaining survivors, with military hospitals on full alert, the Greek government spokesman said.

One of the youngest victims was believed to be a six-month-old baby who died of smoke inhalation, officials said. At least 187 people were injured, among those 23 children.

-with agencies