Three Athens bank employees died yesterday in a blaze started by a petrol bomb thrown as the city erupted into violence during a march by tens of thousands of striking workers.

The Greek prime minister, George Papandreou, called the deaths of the two women and one man, who became trapped, “a murderous act”. He said he would not be deterred from pushing through spending cuts and tax rises demanded as part of the €110bn ($141bn) rescue package agreed with eurozone neighbours and the International Monetary Fund.

The fire broke out in a branch of the Marfin Popular Bank. Officials said the three died of asphyxiation. The attack came amid growing anger at a round of austerity measures launched by the socialist government in return for emergency loans to tackle its debt crisis.