Police forces in Greece have clashed with thousands of protesters outside parliament in central Athens during demonstrations over a train crash that left nearly 60 people dead in late February.
Some 10,000 people, including students and railway workers, gathered at a square on Sunday to demand better safety standards on the rail network.
"That crime won't be forgotten," protesters shouted as they released black balloons into the sky. A placard read, "Their policies cost human lives."
At least 57 people, including several university students, died when a passenger train slammed into a freight carrier on February 28. The train, traveling from Athens to the northern city of Thessaloniki, was packed with university students returning after a long holiday weekend.
Railway workers who also lost colleagues in the accident have staged rotating walkouts over the past few days to denounce cost-cutting and underinvestment in the rail infrastructure.
The government has blamed human error and a railway official faces manslaughter charges.
Prime Minister Kyriakos said in a Sunday post on Facebook, "As prime minister, I owe everyone, but most of all the relatives of the victims, an apology. Justice will very fast investigate the tragedy and determine liabilities."
Railway workers' unions say safety systems throughout the rail network have been deficient for years as a remote surveillance and signaling system has not been delivered on time. They have called on the government to provide a timetable for the implementation of safety protocols.