At least five of those who died were killed as they tried to escape from the flames into the sea.
Meanwhile in addition to the rising death toll, a number of people have been reported missing, some of whom are said to be tourists. Of the at least 94 people injured, 11 were in intensive care, and 23 were children, they added.
Among the dead is a group of 26 travelers - families, including children, who were found in a final embrace at a seaside resort in Mati.
There were fears the toll may rise further, as people remained unaccounted for.
The wildfires started in the Attica region, about 18 miles from Athens.
Greek authorities urged residents of a coastal region near Athens to abandon their homes as a wildfire burned ferociously, closing one of Greece's busiest motorways, halting train links and sending plumes of smoke over the capital.
A helicopter drops water to extinguish flames.
A house burns during a wildfire in Kineta, near Athens, on July 23, 2018.
The U.S. Embassy in Athens - which issued alerts about the unsafe fires on Monday afternoon - says American fire experts are visiting Greece to meet with fire officials to discuss how U.S. agencies can help.
Giorgos Mathiopoulos, the head of Greece's emergency workers association, told reporters that one fire broke out around noon and the second around 5 p.m.
A view of burned cars after a fire in Argyra Akti, Mati, close to Nea Makri, in Attica, Greece, July 24, 2018.
Terrified survivors have described the chaos that broke out as "Biblical" wildfires devoured an entire Greek village in a matter of minutes.
Firefighters carry a dead person following a wildfire at the village of Mati, near Athens, on July 24, 2018.
"Everyone should keep their temper and take care to protect the most precious good that is human life", he said.
Teen Killed, Sister Wounded In Train Station Stabbing Attack
BART resumed normal operations Monday morning but passengers expressed concern about riding while the suspect is still at large. Cowell pulled a knife and a replica gun on a supermarket clerk who confronted him over stealing, court records show.
North Korea reportedly dismantling key missile launch site
Jack Keane said while it may be a step in the right direction, it may not be the kind of progress the USA should be making. The 1950-53 Korean War ended with an armistice rather than a peace treaty, leaving the two Koreas technically at war.
Ivanka Trump shutting down fashion brand
Nordstrom parted ways with the brand, which was launched in 2014, as far back as February 2017, citing "brand performance". Trump claims that her work in Washington and potential conflicts of interest are impeding her eponymous company's growth.
"The night will be hard", civil protection chief Yannis Kapakis told Ert which cancelled its normal programmes to cover the fires.
The wildfires have affected the area of Attica, but has not affected other popular islands such as Crete, Rhodes and Zante.
Dimitris Tzanakopoulos said that at least 69 other people have been hospitalised with injuries.
How badly burnt is Mati?
Evacuees were transferred to hotels and military camps, while anxious relatives flocked to the area.
"Residents and visitors in the area did not escape in time even though they were a few metres from the sea or in their homes", fire brigade spokesperson Stavroula Maliri said.
On Monday, the Nordic nation's civil protection agency MSB said there were 27 active fires across the country, as temperatures were expected to soar as high as 35 Celsius this week.
At least 220 firefighters were on the scene while five water-dropping planes and seven helicopters helped to fight the blaze from the air.
Fueled by 80 kph (50 mph) winds that frequently changed direction, the fires ‚one to the west of Athens near the town of Kineta and another to the northeast near the port of Rafina, spread at speeds that surprised many, trapping hundreds on beaches and cutting off escape routes.
"Today, Greece is in mourning", said Greece's Prime Minister Alexis Tsipras, who cut short a visit to Bosnia and announced three days of national mourning.
Near the town of Marathon, residents fled to safety along the beach, while 600 children were evacuated from holiday camps.
"I am really concerned by the parallel outbreak of these fires", he said, with officials raising the possibility they could have been started deliberately by criminals out to ransack abandoned homes. "Burning pine cones were flying everywhere".
Forest fires are common in Greece during the hot, dry summers and the country has been facing high temperatures recently of up to 104 Fahrenheit.