Twenty-six people were killed and at least 85 injured after two trains collided head-on in Greece late on Tuesday night, the fire brigade said, while the circumstances of the crash remained unclear.

An intercity passenger train traveling from Athens to the northern city of Thessaloniki collided with a cargo train outside the city of Larissa in central Greece, said the governor of the Thessaly region.

"The collision was very strong," governor Konstantinos Agorastos told SKAI TV, adding the first four carriages of the passenger train had derailed.