STORY: Gale-force winds and thick smoke hindered fire-fighting efforts from the air and on the ground. Ambulances took three people to hospital due to respiratory problems and light burns, according to authorities.
The wildfire broke out around 1430 GMT on Tuesday some 27 km (16 miles) north of central Athens and was still burning on several fronts. The billowing smoke was visible from the island of Evia some 50 kilometres away.
Penteli suffered a wildfire in July 2018. Huge wildfires in 1995 and 1998 burned more than 13,000 hectares over three days.
Fire fighters recovered the body of an 84-year old man who died from shotgun injuries, police said. A fire brigade spokesman said he was found in his burning home and he probably committed suicide but the incident was under investigation.
About 485 firefighters and 120 fire engines were deployed to tame the blaze, which kept burning on several fronts. Nine aircraft and 10 helicopters were dumping water on the flames on Wednesday.
In a televised statement, Fire Department spokesperson Yiannis Artopios talked of a "difficult night," as wind speeds exceeded 80 kilometres (50 miles) per hour, constantly changing direction, hindering efforts to tame the blaze.