The Greek prime minister's bid for re-election at forthcoming polls may be thwarted by the country's deadliest train crash, which has sparked mass protests and calls for him to quit.

A nation heartbroken at the loss of 57 lives has exploded in anger, with tens of thousands taking to the streets on Wednesday in sometimes violent protests.

Four people -- three station masters and a rail supervisor -- are facing multiple charges over the head-on collision on February 28 and could be jailed for life.

But public anger has focused on mismanagement and underfunding of the railway network, which critics say is symptomatic of a broader hollowing out of public services that was triggered by the country's debt crisis.

And, observers say, conservative Prime Minister Kyriakos Mitsotakis -- who had looked on course to comfortably win a second term -- may pay a heavy price.

The accident "will have an impact on the government, as it has political and ethical responsibility", Stella Ladi, who works at Panteion University in Athens and Queen Mary University of London, told AFP.

During Wednesday's protests in Athens, the biggest the capital has witnessed since demonstrations some years ago in the wake of the eurozone crisis, anger among protesters was palpable.

"People have been under pressure since the financial crisis," Pinelopi Horianopoulou, a striking civil servant who joined the protests, told AFP.

"There are not enough staff."

Understaffing had been a key complaint of railway unions, who had long been ringing alarm bells about the parlous state of the nation's infrastructure

Main opposition leader Alexis Tsipras said on Friday the government had not paid any heed to their repeated warnings over the past two years.

The former left-wing prime minister also accused the government of trying to dodge its responsibilities, after Mitsotakis said that past ruling parties should also share the blame.

"This is a cover-up attempt," Tsipras said.

- Political uncertainty -
 

But all mainstream parties that have held power in recent years -- Mitsotakis's conservative New Democracy, Tsipras's Syriza and the socialist PASOK -- could suffer losses at the ballot box, Ladi said.

There could be "a protest vote against ruling parties of the last decade, which were unable to address public sector failings", she said.

Mitsotakis was elected in 2019 and, before the train crash, his party held a 7.5-percentage-point lead over its closest rival, Syriza.

The latest opinion polls on voting intentions suggest that while his party is still ahead of Syriza, that lead has narrowed since the train disaster. One poll of 1,241 people carried out last week gives ND 29.6 percent of voting intentions to 25 percent for Syriza.

The 55-year-old premier's term ends in July and he had already been out campaigning this year, criss-crossing the country and saying the "countdown" to the election had started.

He had been widely expected to call a ballot on April 9 but, following the backlash triggered by the accident, analysts believe he will delay the vote, possibly until the end of May.

He seems keen to avoid the question for now. Asked when the election date would be set, government spokesman Yiannis Economou said this week the issue was "not on the prime minister's mind at all".

Ladi said the government's priority currently was "the adoption of measures to comfort victims' families and restore the railway network".

Criticised for intially trying to blame the accident on "human error", Mitsotakis sought forgiveness at the weekend from the victims' families and apologised. But his words were widely judged to have come too late.

For many observers, when it comes to what will happen in the forthcoming election, all bets are now off.

"No political analyst is now risking predictions" about the election result, said daily Ta Nea, adding that the chances of a single party being able to form a government were weakening.