Video footage on Greek websites showed one carriage had ripped through the ground floor of a two-storey house. Other photographs showed carriages with smashed windows and others on their sides in a residential area.
The train was heading from Athens to the second-biggest city of Thessaloniki when it derailed in the town of Adendro, some 37 km (23 miles) away. The cause of the accident was not clear.
The driver was in critical condition, TRAINOSE said.
"Death came calling," the Athens News Agency quoted Yorgos Mylonas, a local resident, as saying. "I heard a strange noise and then I saw the train approaching and rammming into my neighbor's house," he said.
The agency reported about 100 passengers were on the train and some media said five carriages had derailed.
At least 12 fire trucks were deployed to the area, the fire brigade said, and a rescue operation was underway.
