The economic crisis enveloping the debt-stricken country not only claimed its first lives: it shifted from bewilderment into violence

At 2.03pm today, on the third floor of a neoclassical building in the heart of Athens, three people died – and Greece changed. As the bank employees tried to beat back the flames, ignited by a firebomb tossed into the building by protesters, the economic crisis enveloping the debt-stricken country not only claimed its first lives: it shifted from bewilderment and disappointment into violence carried on an unpredictable current of rage.

The young bank employees, a man and two women, one of them four months pregnant, died in the fire which came within an hour of irate protesters laying siege to the Greek parliament.

"All of us are angry, very, very angry," bellowed Stella Stamou, a civil servant standing on a street corner, screaming herself hoarse, a block away from where the bank had been set alight.

"You write that – angry, angry, angry, angry," she said, after participating in one of the biggest ever rallies to rock the capital since the return of democracy in 1974. "Angry with our own politicians, angry with the IMF, angry with the EU, angry that we have lost income, angry that we have never been told the truth."

Across Athens today the signs of that anger were everywhere: in the central boulevards and squares that resembled a war zone, the burning cars, the burning hotels, the burning government buildings and rubbish bins and shattered windows and pavements.

Surveying the debris, Karwan Ahmet a 28 year-old Iraqi Kurd caught up in the chaos, described the scene as "being straight out of Iraq. It reminds me of all the shit we saw in Kirkuk."

What had started as a general strike called by unions to protest against deeply unpopular austerity measures turned into a tidal wave of fury as an estimated 100,000 private and public sector workers took to the streets screaming "let the plutocracy pay".

By midday that rage had assumed a new and determined dynamism as demonstrators – including once-stalwart supporters of the governing socialist Pasok party – began to shout "thieves, thieves".

Their venom soon turned towards the large sandstone building that is the Greek parliament. After scuffling with police, chasing the ceremonial guards away from the Tomb of the Unknown Soldier and taking axes to the monument, hundreds tried to storm the building, screaming "let the bordello burn".

As MPs inside debated the draconian economic reforms that eurozone nations and the IMF have demanded in return for the biggest bailout in history, riot police outside fired off rounds of acrid teargas to keep the crowd at bay. "All of them are dirty and have eaten from the trough," said one man brandishing a large wooden club. "Our politicians are squarely to blame and the worst of the culprits know it because they have fled the country."

With Greece facing a 19 May deadline to refinance its staggering €300bn euro debt, the EU and IMF agreed last week to inject up to €120bn euro into its cash-starved coffers on condition that Athens makes unprecedented budget cuts.

The tough regime, which also includes a freeze on public sector wages and pensions in addition to tax hikes, has not been seen since the country emerged from the privations of civil war in 1949.

"Why should we, the little man, pay for this crisis?" said Giorgos Didimopoulos, a 55-year-old jeweller who belongs to a communist-backed union which on Tuesday stormed the ancient Acropolis to make precisely that point.

"What people forget is that we Greeks don't like authority. We have always resisted when we think something is unfair. We fought against the Persians at Marathon, the Germans during the second world war and we will fight the IMF because in reality we no longer have a government. It is foreign forces who are in charge of us now."

Polls show that he is not alone. The perception is growing that it is low-income Greeks, already hit by three previous packages of austerity measures, who are being made to suffer disproportionately from the three-year fiscal and structural programme. In repeated surveys the vast majority have said they will take to the streets to oppose the "barbaric" measures. For many, today's violence is a taste of what is to come.

With unions backing the general strike – a walkout that crippled the country and isolated Greece from the rest of the world – the protests were seen as a key test of prime minister George Papandreou's determination to carry out the reforms. Germany, which will be picking up the lion's share of the emergency aid, has been quick to warn that if Athens strays the money will dry up.

But he clearly has a battle on his hands. "No longer can they say that these are isolated incidents of violence carried out by stone-throwing anarchists," said Makis Papadopoulos, who owns a popular tourist store in the capital's historic Plaka district where shopkeepers were fearfully boarding up premises.

"People are being pushed to the hunger line. With the intervention of the IMF things have changed. We now have an explosion situation and no one knows what the limits of Greeks are, how far people will go to vent their spleen." Resolution, say some, will only come with a root-and-branch clean up of Greece's corrupt political system.

Papadopoulos said: "This crisis has taught us that we can't go on acting the way we did, living off loans, treating the state as an endless treasury to be raided, never thinking about our future."