Fast-flowing torrents of red mud flooded roads.
And that's not all.
"Everything is destroyed, destroyed in biblical proportions", Mandra mayor Yianna Krikouki told the state news channel ERT.
Older people who were found dead inside their homes were also among the casualties. "It is the wish of all of us that this number does not increase", Prime Minister Alexis Tsipras said in a televised address, announcing a national day of mourning Thursday.
That has been forced upwards by the mountains in northern and western Greece, causing torrential rainfall and flash flooding there. The body of another man was later found in the yard outside a local business.
Further storms are expected to hit western Greece in the coming days.
Sky News Weather Producer Rebecca Yussuf said the extreme conditions have been caused by a persistent cut off low and strong Scirocco winds. An additional two were later detected by coastal guards after they were swept away by the floodwaters.
Residents and news outlets reported overflowing rivers that flooded roads, vehicles and buildings.
"The weather forecast is poor, so we are on alert", he said, adding that "torrents of water" had flooded a highway all the way to the sea many kilometres (miles) away. Investigators would be looking into whether factors such as shoddy or illegal construction might have contributed to the severity of the flooding.
Locals walk through the flood damage in Mandra, northwest of Athens, Greece.
A state of emergency was declared in the small Aegean island of Symi, close to the Turkish coast, after heavy rains flooded homes and shops and created electricity cuts when the local power station was flooded.