Many people have taken to the streets with black balloons. The demonstrators are holding posters with slogans "Killers! Privatization kills!", "This is not an accident. This is a crime," and chanting "You are counting income, while we are counting the lost lives."

"My father [a railway worker] said that trains were falling apart and they should be written off, it was dangerous to travel in them, but they were still operating … These problems have been accumulating for years and they have not been solved," the protesters cited letters from railway employees and their families as saying.

The rioters also stressed that there were not enough railway personnel and that people were "working themselves to the bone," as stated in the letters.

On Tuesday, a passenger train collided with a freight train near the city of Larissa.

The passenger train had switched to the freight train's lane before the accident, which brought them both on the same track and resulted in a head-on collision.

The Greek police said that 57 people had been killed and 48 others injured in the accident.

Media reported on Saturday that EU prosecutors had been probing a contract that would have had an electronic control system installed on the Greek railways, potentially averting the train wreck, if implemented.

The upgrade to the signaling and remote control system on the Athens-Thessaloniki-Promachona railway was agreed in 2014, but a series of thefts and acts of vandalism stopped the contract's implementation in its tracks, the reports said.