Masked youths threw petrol bombs and clashed with police outside the Greek parliament on Friday, as huge crowds gathered in a show of force to mark the second anniversary of the country's worst rail tragedy.

Nearly 200,000 people gathered to demand justice for the 57 victims of the crash between a freight train and a passenger train near the central city of Larissa on February 28, 2023.

But much of the crowd, including children and the elderly, was forced to flee when hooded and masked attackers hurled petrol bombs and rocks, prompting riot police to fire teargas and stun grenades in response.

Police then deployed a water cannon as the youths set fire to bins and vandalised bus stops and shop windows. Over 40 arrests were made.

The ambulance service said nine people were taken to hospital, including a photographer hit in the head by one of the grenades. 

Several were treated for their injuries in parliament.

"The crowd was extremely packed and many panicked," protester Sofia Yianniri told AFP. "We tried to get people with children out."

When the peaceful protest resumed, many shouted "murderers" while there were also cries of "justice" and "resign", apparently directed at Prime Minister Kyriakos Mitsotakis.

Opinion polls indicate that most Greeks believe officials covered up vital evidence following the crash, slowing down an investigation that is still incomplete.

"The truth will emerge and justice will come, bringing plenty of oxygen for ourselves and our children," Tempe Victims' Association president Maria Karystianou, whose daughter was killed in the crash, told the crowd.

'Strong message'

Police earlier said some 325,000 people had protested nationwide. Packed subway trains in Athens forced many to walk several kilometres to join the crowds.

"Today we must send a strong message to punish those responsible for this tragedy," Nikos Lykomitros, a 20-year-old archaeology student, told AFP. 

Babis Solakidis, a 44-year-old metalsmith, added: "This was not a simple accident, and there will be more if safety measures are not taken."

Schools, many shops, public services, trains, ferries and most flights were shut down, with protests in other European countries and cities worldwide with large ethnic Greek populations, such as New York and Melbourne.

In a rare move, justice officials held a moment of silence and a one-hour stoppage before midday Friday in memory of the victims. 

Several prominent artists joined the walkout, shutting down theatres and music clubs.

Over 40 people have been prosecuted, including the local station master responsible for routing the trains, but a trial into the tragedy is not expected before the end of the year.

The two trains had travelled towards each other on the same track for miles without triggering any alarms. The accident was blamed on faulty equipment and human error.

The government has rejected accusations by opposition parties that it was behind an "organised plan" to shield senior officials from responsibility.

"Society is angry because society has been misled," government spokesman Pavlos Marinakis said this week.

"One of the aims by a large part of the opposition is to lead to tension, to an explosion, through misinformation," he said.

No-confidence vote

Opposition parties will call a no-confidence vote against the government next week, in addition to a parliamentary inquiry into whether officials were too quick to bulldoze the disaster site and, as a result, destroyed vital evidence after the collision.

Mitsotakis, who has dismissed calls to resign, has accused critics of attempts to "destabilise" the country and "sink political life into a quagmire".

He has long been criticised for hastening to attribute the accident to human error just hours after the official investigation began.

An experts' report funded by the victims' families has claimed the freight train was carrying an illegal and unreported load of explosive chemicals, which contributed to the high death toll.

On Thursday, Greece's state aviation and railway safety investigation agency said there was a "possible presence" of an "unknown fuel" at the scene.

The train's operator, Hellenic Train, has denied knowledge of any illegal cargo.

Τhe Athens prosecutors' office has summoned Hellenic Train's former CEO Maurizio Capotorto on suspicion of giving "false testimony" to a parliamentary investigative commission last year.

There is also broad scepticism over the unexpected emergence of camera footage allegedly showing the freight train on the night of the accident, apparently showing no unusual containers.

Under privacy laws, surveillance videos are supposed to be automatically deleted within two weeks of filming.