The unfortunate incident took place around 1 o’clock in the afternoon local time (11:00 GMT+1) in the center of the village.
The girl was riding her bicycle when the bus, which was carrying no passengers at the time, struck her.
The nine-year-old girl was immediately transported to Thessaloniki’s Hippocration Hospital.
After her initial medical examinations, the doctors sent the victim to the intensive care unit of the hospital, since she is suffering from serious head injuries.
Vassiliki Papachristodoulou, the director of Hippocration Hospital, told the press that the girl’s condition is now viewed as serious, but stable.
The local police authorities in Serres are now conducting an investigation into the exact circumstances of the incident.