ATHENS, Greece (AP) — Thousands of people protested on Sunday against safety deficiencies in Greece’s railway network nearly two weeks after dozens were killed in the country's deadliest train crash.

The demonstrators also demanded punishment for those responsible for the head-on collision between a passenger train and a freight train that killed 57 people Feb. 28. Police said that more than 8,000 people in Athens gathered outside Parliament to protest on Sunday.

The protesters later marched to the offices of privatized train operator Hellenic Train. The company, which has been owned by Italy’s Ferrovie dello Stato Italiane since 2017, isn't responsible for the maintenance of the railway network. State-owned Hellenic Railways is in charge of upkeep.

Authorities shut down four subway stations on two lines running through central Athens because of the protest.

The rally was organized by civil servants, a pro-communist union and university students.

In Thessaloniki, Greece’s second-largest city, about 5,000 people demonstrated, listened to speeches and shouted slogans, such as “we will be the voice for all the dead.”

Sunday’s rallies, which passed off without serious incident, weren't as well-attended as similar events earlier in the week, when more than 30,000 had turned out in Athens and more than 20,000 in Thessaloniki. Police said four people were detained in Athens.

A memorial service was conducted for 12 students of Thessaloniki’s Aristotle University, Greece’s largest, who were killed in the train crash.

An inexperienced stationmaster accused of placing the trains on the same track has been charged with negligent homicide and other offenses, and the country’s transportation minister and senior railway officials resigned the day after the crash.

Revelations of serious safety gaps on Greece’s busiest rail line have put the center-right government of Prime Minister Kyriakos Mitsotakis on the defensive. He has pledged the government’s full cooperation with a judicial inquiry into the crash.

Elections are due later this spring and opinion polls released over the past week have shown the ruling conservatives’ lead over the left-wing opposition shrink almost by half compared with polls published before the crash.

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Srdjan Nedeljkovic in Athens, and Costas Kantouris in Thessaloniki, contributed to this report.