The cause of Greece's deadliest train crash in decades remained unclear. People were on their way from Athens to the northern city of Thessaloniki at the time of the collision.
Trains were hurtling towards each other on the same track.
The first four carriages of the passenger train were derailed in the crash, while the first two carriages, which caught fire, were 'almost completely destroyed', Thessaly regional governor Konstantinos Agorastos told SKAI TV.
People at the scene of the disaster describe panic and screaming.
Approximately 250 passengers were evacuated to Thessaloniki by bus and were evacuated safely.
According to local media reports, around 350 people were on board the passenger train, which was on its way from Athens. Just before midnight on Tuesday, the fire service said it was informed of the accident. The freight train had been on its way from Thessaloniki to Larissa.