ATHENS: A 65-year-old man died from heart failure during a demonstration in Athens Thursday where riot police fired tear gas to repel firebomb-throwing protesters, a health ministry official said.

"A 65-year-old man was taken to hospital where efforts to revive him failed," the official told AFP, adding: "There were no bruises on his body."

A police source said the man had been picked up from a bench in front of a church - several hundred metres (yards) from the area where the clashes took place - while other reports said he had been found on central Syntagma Square, close to the scene.

Initial reports said the man was 66 years old.

The ministry official said two people had also been injured in sporadic clashes that broke out around Syntagma Square during the protest against a new wave of austerity cuts that the government is preparing to introduce next month.

Tens of thousands of people took part in the Athens protest while a smaller demonstration was held in Greece's second city Thessaloniki.

Last year, a 53-year-old builder similarly died of a heart attack at another anti-austerity protest though police denied that tear gas was to blame.