NEW : Police estimate 500 people turned out for a peaceful protest in Athens . A 31.5 billion - euro bailout installment is due from the European Union and Japan . The Greek parliament is required to pass new emergency legislation beforehand . Local media say the vote will be a surprise , with narrow passage expected .
NEW : Police estimate 35,000 people turned out for a peaceful protest in Athens . A 31.5 billion-euro bailout installment is due from the European Union and IMF . The Greek parliament is required to pass new austerity measures beforehand . Local media say the vote will be a cliffhanger , with narrow passage expected .