Tens of thousands of furious protestors have taken to the streets as politicians prepared to pass legislation introducing a package of pay cuts and tax hikes.
Protestors, reportedly from communist groups, attempted to storm the parliament to prevent the socialist government from rubber-stamping the austerity package agreed on Sunday as part of a bailout by the EU and IMF.
Riot police kept protestors at bay using tear gas, pepper spray and stun grenades.
Molotov cocktails and stones were hurled at police as demonstrations grew out of control. At least two buildings were set on fire during clashes, with three people found dead after a bank went up in flames.
Police had earlier denied agency reports of deaths at the bank, but the fire brigade confirmed that three bodies were found in the wake of the protest.
"We have found three dead people in the building that is on fire," the fire brigade said in a statement.
Greece has a record of resistance and popular protest but today's violence has sent shock waves through financial markets fearful that the Greek public will not stomach the hardship that comes with the aid package.
Today has also seen a wave of strikes across the public and private sectors as stock markets plummeted.
(EurActiv with agencies.)