The car which was parked on the sidewalk facing the central bank building blew up around 0825 IST. The building is close to the office of Greece's international lenders.
Police said the car, a Nissan, had been stolen and was fitted with 75 kilos (165 pounds) of explosives.
Internet news website Zougla and the Efymerida ton Syndakton newspaper had been informed of the planned attack by telephone one hour before the explosion.
Greece announced yesterday it would return to the debt markets on the same day protesters launched the first anti-austerity strike of the year, crippling key services across the country.
Athens' move was welcomed by the International Monetary Fund, which along with the European Union and the European Central Bank has provided monetary support for the troubled economy.